Newbie here feed tube question

I am planning several rocket burners for different things. My question is, has a long feed tube been tried with a cap? Feed into the burn chamber from above, fire distance correct from secondary combustion chamber,  but long tube and cap it, let the air in like a tunnel feed type thing?  Wouldn't the cap let longer material be used without being able to chimney?  I've seen all the arguments for short feeds and understand, like the idea of slanting a long tube both for ease of loading and "flow" of material into the fire.   Still makes me think a longer time between loading could be achieved by capping the tube...   Newbie here, just starting to play with this, you don't have to be gentle... LOL

It has been done, the fire still burns up the feed tube, you need to let air in another way, and as far as I know none of the acknowledged experts advocate this.
Batch box and pellet fed rockets are other ways to make them more hands off.
Best capped feed tube design  I've seen was a outdoor rocket boiler on YouTube.

 Thanks, if they know it burns up the closed tube, I believe them, I can understand why, with the air coming in from the end it would ventilate any tube big enough to hold a lot of wood... makes sense. SO... how long a feed tube is safe max? I'm thinking I need a six inch rmh for my garage, what's safe ?

 Thanks so much for all the help!

One third of the heat riser height (measured from burn tunnel floor) will probably be safe as long as the burn tunnel is as short as you can make it while fitting necessary clearances. A ratio of 1:1.5:3 (feed to burn tunnel to riser) measured along the outside edges of the cavity is good, as long as you have decent draft.