Rivnuts seem to be working pretty well... have done more than a few and have never had anyone report back an issue. If you want to run up here sometime we can pop some in for you, lmk.
And for whatver reason, the rear towers seem to be the most prone to falling in, at least for me lately. but if I alternate on the bolts, backing each one up nice and gently, I can usually get those factory nuts to stay put long enough to put the new tower on. But when I remove one bolt completely, then start in on the second bolt, almost without fail that factory carrier will start to spin, especially in back. Also the 200's are much more delicate than a GX460 or 4Runner, can get away with being a little more aggressive on those. No idea why, as it all looks like the same set of parts.