Actually, you should check the pics at the bottom of this page, which I posted as soon as the TPRO was released:
http://www.o-review.com/forum_detail.asp?ID=5232&StartNum=17
You can see that the outside corners of the lens don't match up (like the R2 with HJ lenses). Using XLJ lenses makes it look a lot better (because they curve back out to the outside). Anyway, the fit along the top is very similar to the stock lenses, and I wouldn't worry about them falling out.
Bottom line: If you've got the lenses already, they'll make a suitable substitution. Same deal if you really want a color that isn't made yet for the TPRO. But be advised that the fit does have gaps at the edges (which may be enough to dissuade some of the more anal retentive among you).