I checked the HT-DT assembly and it matched up with the drawing nicely. The next step was to cut the compound miter at the bottom bracket shell. I had already cut the miter for the BB, but I had to cut the notch for the seat tube. This ended up being a tough one... there was a lot of back and forth between filing the miter and checking the fit. In the end the best approach was to use the jig. With the BB-ST assembly held solidly in the jig I could quickly install the HT-DT and check for fit and angle. Finally I reached a point where it was as good as it was going to get, and I prepped it for brazing.
After the brazing was done and the frame got a soak, I checked the frame against the drawing. It ended up needing a bit of cold setting, and I was surprised at how little pressure it took to make adjustments to the frame's geometry. It isn't perfect, but every time I do a frame check I'm pleased at how well the frame is turning out.
Like I said before, the DT-BB-ST was a tough miter, but in general I think I'm getting better at mitering tubes; the top tube went much smoother.
With the front triangle together, the frame is about 1mm shorter in length than planned but all the angles are within 0.1 degree of where they should be with the bottom bracket shell and lower end of the head tube lined up with the drawing. How the overall alignment comes out remains to be seen. The BB isn't faced yet (I'm waiting until I get the chainstays installed), but at this point it looks like there is a bit of twist around the BB-ST. I don't expect it to be anything major, especially for a first frame that only I'll ride.
Next up, the chainstays. This should get interesting...