After spending some time yesterday drilling the seat back angle to size, I finally got to put the center seat section in today. The back torque tube support fits perfectly and rests at 90-degrees like it's supposed to. I'm going to wait to drill the ssupport to it's final position until I can get to it better. I did uncover a mistake though. Apparently my 1-1/8" hole saw doesn't run true and cuts holes 1-3/16". I tried putting the torque tube in there for a quick fit, and there was all kinds of slop in the fit. I guess I'll have to get a different 1-1/8" hole saw and re-make those torque tube bearings. Oh well, I certainly know how to make parts. No worries.