I felt under the weather all week last week and didn't get much done, but RP was kind enough to do what they could to check the torsion tubes they had in stock by validating that they fit with their transmission mounts, which I really appreciate. Even though I haven't had good luck with the parts, their support has been excellent.
I still think that my measurements of my torsion tube are correct and that either they have a good one in stock or the transmission mount they have is also off or has larger tolerances. I ordered a new transmission mount from our host to see how it lines up with my torsion tube, since that costs about the same as sourcing a torsion tube from another supplier and then I'll have new transmission mounts.
I spent the weekend in Greenville, SC at BMW's 2-day driving course. I feel good that I acquitted myself well as the only person there that didn't (currently) own a BMW. It will be interesting to see how well what I learned in the FR and AWD cars translates to the GTi's FF layout and whether I recall any of it by the time the 911 is back on the road.