I just started reading the thread, and need to go to bed, but I'll be back to read the middle pages. Congratulations on the shed build, I got to where you were using the OSB for the inside and the scavenged SIP's (not very far). Then I went to the end, before I crash for the night. I saw the bike you made for yourself, the MTB top tube looks more like a 'mixte' frame than a double-diamond traditional safety bike frame. Those seat stays are very-curvy, hard to do from what I know. Is that frame chro-moly? The frame at the end of your thread has beautiful welds, but looks like Ti to me, rather than chro-moly. The seatpost on the bike in your #3 post looks like it wouldn't stand-up to my 'Clyesdale' class weight on it, that's a lot of unsupported tubing. I estimate it's close to 21 inches from the crank shell to the seat rails.
I have a vintage Klein Attitude I bought new in 1992, it cost almost $3K, I spec'ed it with Deore XT when that was the best Shimano gruppo, and when XTR came-out the next year, I had that replace the XT, which I put onto another backup bike. The Klein was built before Gary Klein sold the company. I'm a 'retro-grouch,' I don't have any suspension front or rear, not even an elastomer seatpost.
I also have a Litespeed Classic roadbike, and when I sent the bare frame in to have it checked-over, many years ago, they asked me, "where did you get this?" I bought it as a bare frame from the same FL dealer from-whom I bought the Klein, new. They told me, "that's the 19th frame we made!" As you probably know Litespeed makes frames in Ti for other manufacturers.
I know there will be lots of interesting info on the pages in-between where I just began, and ended, thanks for posting your work on the property. I get lots of ideas from the website, and sometimes it's just fun to see how other members meet their challenges.