Ineed frame tie advice for the '67 fastback please!

I have the US car tool conectors in my car. Took alot of fitting as my car is a rag top. But the finished product looks like a full frame, and made the car very stiff, for a better feel.

See, those are the ones that I saw previously, but did not bookmark. I like the way they involve the floorpan in the welding process and help stiffen both the flex there as well as making the subframes unable to flex at the undercar endpoints. . .and I have seen mine flex more than I thought it would while I was placing jackstands under the frame and behind the front wheel. And, yet. . .any potential for vibration cracks at those spot welds? Is the metal about 18-20 gauge, same as the floor itself and depending on its shape for rigidity? I've wondered that too.

With a ragtop, they also put in front or front and rear stiffeners (triangle shaped) at the subframe endpoints outward toward the rocker panel and quarter panel lower edge I've seen. "Charlie" (daughter's ragtop) only seems to have the front stiffeners.

Just how much "fitting" did you need to have done J? I would love to see pics of the process if you still have some.