Hi Bob, I guess I'll be the second one to welcome you to the forum. Personally, I think the 12 inch tires are getting a bad rap. Both of my teardrops are built on a Harbor Freight trailer and have 12 inchers. I usually cruise along at 65 or 70, depending on the concentration of law enforcement. (Our Calif law forbids towing any faster than 55 mph.) I think the 55 recomendation on the tires is a CYA statement. I have never had a tire failure, and after 30,000 miles on my 450 lb woody, I have bought 2 new sets of tires, not because they were in danger of failing, but simply because I wanted to feel safer as I crossed the deserts, mountains and praries from Calif to Indiana and Kentucky.
I suppose those with heavier trailers wouldn't agree with me, but for my weight and mode of travel, 12 inch tires work just fine. I always carry a spare wheel and tire, just in case. Good luck on your build, you failed to mention where you are from, but surely there must be some TDers in your neck of the woods, just put out the word, and you will surely get in invite to swing on by and check their trailers. Check with the Tearjerkers website, they are all over.

Roly, the li'l ol' So Calif TD builder and user.