Hey Mike!
Thanks for sharing the video, very nice to see.
(Fred M. and Izzy if you ever need a timber frame or one of my other eclectic skill sets I would love to come back down to the "real south" for a stay... Fred M. sorry if I am about to counter some of your advice in any way...apologies)
Mike, among my many eclectic skill sets, I am a sawyer, arborist, logger, and woodcrafter in several folk traditions. I have owned (own) several chain saw mills (up to 3 m or 8 feet but now only a 1.6 m) several band mills, a couple of swing blades, and started as a "pit man" before becoming a "tiller," in the true traditional methods of making plank. I have done this with both European and Asian modalities of hand sawing, as well as,
water mill circle and sash mills. So your idea of taking a "properly rigged" chain saw and "board racing" (or ripping" with it is more than plausible.) I will give you the basic action steps you need to know that are not being shown in the film, and it is not as hard as many will tell you (though slower than a production mill with band, or circle blade.)
Before I start, as disclaimer:
Chain saw and tree work is lethal! Don't think otherwise. The more of it you do, the more bone and flesh you will give to it...I know this first hand. You are going to get cut, no matter how safe you are. What gets you is not the "perceived risk," (fellow in videos are pretty safe not considering going deaf or blind) but the hidden actual risk (bee sting and falling over with saw...been there done that) So just know that you
should take all the safety precautions you can, yet understand you will still get hurt if you do this work for any length of time no matter how safe you are. Protective clothing is good, but I have seen many in the tropics (white men) fall over from heat stroke do to wearing heavy chainsaw protective gear...I don't. I depend on my bone and muscle to keep me away from the blade, and glasses and simple ear plugs for the other to soft spots that need real protection doing this work. You choose according to your comfort level and KNOW the risks. Keep others away, though the fellow standing in front of the chain saw "tending" the "Sawyer" is exactly where he (the "tender") does stand most times (though he should have eye and ear protection.) A chain will not fly off and kill anyone, it just stops spinning 99.9% of the time. "Kick up" is the biggest issue in "board racing" and you will learn that first hand from the "log and the saw" when they teach you this lesson experientially.
Step one:
Get a proper lumber "tree," then make a "log," then section that into "bolts," then rough out your "cants." Don't know the words and what a proper lumber tree is...then read a whole lot or work with a sawyer that has at least 20 year "bush milling"
experience. I could keep writing on step one alone and fill a complete volume of text.
Step two:
Crib your bolt for milling with "dogs" of some fashion (it really should be free of bark at this point especially for beginners.) "Box" your bolt end with a level marking out the plumb and level lines of a cross. Then mark out in ink the outline of the "cant" end you are about to make. Then, from the corner points of your projected "cant," snape a grease line or ink line (chalk blows away) done the bolt to the corner outline on the other end of the bolt. This is the line you are racing (cutting.) Now it is time to "clear the cant from the bolt," by removing the "slab rounds" off the bolt.
Step three:
Prepare for milling the "cant." You must now figure out what you want from the cant, as it could be done now and just have a big timber, or if you want planks, you need to know what size they are to be (don't forget to remember "kerf waste" caused by the thick chainsaw blade.) Also, do not try to cut anything thinner than 30 mm, it just is not worth it. Once you have made your selection, you are going to snap lines that represent the planks, and for beginners (or when I am out of practise) you should also snap extra line that represent the "kerf" left by the cut intself. This will help you stay on track.
Step four:
The milling is going to start soon, and you should have the largest chainsaw you can get with a minimum of a ~ 1 m bar (longer is much better) and it should be slung with a "ripping chain" not a "cross cut." So you are going to have to buy one or "file one out" (the latter takes great skill in sharpening that few I find have.) If you can not hold this machine out in front of you, arms fully extended, with the bar and chain on, and the engine running for at least one half minute you really are not strong enough to do this work safely or efficiently. (get in shape first) If you are a climber, like myself, you have to be able to do this with one arm out to your side, saw at full ideal run, with any saw you climb with, or you are consider deficient in using the saw safely.
Start the saw on the end of the cant between your "kerf lines" you snapped earlier, which now should extend the length of the log and down over the edge on the end of the cant outlineing every thing you are about to cut. Some like to stand straddling the log with their backs toward the direction of pull, while others start this cut facing the end. (the latter can be more accurate but much more risky for "kickup" from the bar.) You are going to "rough in" every board you have outlined on the cant. When you are done "roughing in" you should just about be out of the first tank of fuel and the cant should have the ends completely scored in and the length of the cants should have very straight, neat and clear "kerf channels" or "daddo" to follow when making the planks. I also recommend for beginners that you do both sides of the cant (the outline of the planks) and that your "daddo" are no deeper in the beginning kerfing process than the depth of the chain tooth plus 20 mm give or take.
Step five:
"Freeing the slabs." Now you are ready to start milling some planks, but there is a very important point that many, even what some would call experienced sawyer forget, and that to leave the planks attached to each other until they are all cut out. I leave them attached with a little "relish" of wood on both ends, then role the cant to "clear them off." Remember when doing theis work to leave as much of the bar and cutting chain in the wood as possible to keep things running smooth, straight and true. It is not untill you have "hours" (year?) of experience that you can do what you are seeing in the video, as he is using way too much tip work to be either safe or to produce quality planks, which may have been fine for his goals.
Those are the basics of "racing planks" out of a tree with a free hand chainsaw. I don't think I forgot any thing

but will edit if folks find some missing. There is much, much more to this but you will learn that experientially from the better teach than myself, which is the tree, and your saw.
Good Luck.
j