Hi Vincent,
Last year my garden struggled with vast amounts of precipitation over long periods on clay soil. I participated in a rutabaga trial, with six other rutabaga varieties, and added Eastham to this trial myself. All of the rutabagas did poorly, with many dying out completely, and none of them really being worth harvesting. The Eastham were the only ones that made it and did halfway decent - but were not giant (due to growing conditions). Some would have been worth eating, but I'm saving them for seed production. I harvested them, and they are currently in a box of sand in my
root cellar, starting to put up growth. I plan to plant them out and save seed this season, however, I am close to the bottom of the minimum threshold of plants suggested for a viable population (around 20 plants).
After reading
Joseph Lofthouse's book on Landraces, my longer term goal with Eastham will be to integrate it into a grex/landrace. I got a six species rutabaga grex from Experimental Farm Network this year, so I'll see what happens. At first I will only be able to harvest every other year (unless I magically have time to both harvest and grow out Eastham this year...unlikely), then once I have savable
roots from the best performing of that existing grex, and Eastham, I may lump them together into a
landrace. Time will tell.
I don't think length of season would be a limited factor for you, but I could be wrong.
As to the trouble of getting the seeds: someone very kind, here on permies, helped me out, and mailed the seeds to me. It was a bit of a hassle (and kind of funny - because the person didn't have paypal, I was going to send cash, but only had coins in US currency, which was going to cost more to mail than the amount I was sending! I had a family member with some paper dollars, so was able to send that in the end.) but I'm happy to be toying around with the seeds.
At the end of the day, the kind funds we put into our growing passion projects can be looked at as wasteful if the experiment doesn't work out, or really pretty small investment if they get you excited and have good results. I tend to often go for it, even if it turns out a rat ends up eating all my hardy palmetto seedlings immediately after germination (true recent story that's still sort of stinging.)
By the way - though I didn't grow gilfeather in the trial I was in, others did, and I remember being surprised that it was rated by far the worst tasting of the ones trialed. That could of course come down to many factors, including strain of seed being grown, but because it was across Canada, and many different soils and growing conditions, I would be cautious before growing that one as your only rutabaga variety. There may be very specific ways to grow it (or climates more suited for it) for it to be great, or sometimes this comes down to taste preference.
As to starting rutabagas/turnips early and transplanting - I did not have success with that last season, but have read in some places that it can be okay, if you are very careful during transplanting not to disturb the root.