Tarnished,
I'm not sure if this was the intention, but that link redirects to a forum discussion about the infamous F-16 vs F-35 BFM fallacy. There's some quite good thinking going on there, but as always folks are trying to reverse engineer the F-35s performance tables from those of the F-16 and 18.
I think it's probably fair to say that we know the F-35 g-limits and we've seen the reduced sustained g figures and we are not talking anything particularly dazzling. It wold not be difficult to find a trainer that would match that performance. The new trainer won't just be there as a lead in to F-35 and I would expect the higher g requirements to come from other, higher performing platforms.