I agree with CM. The F-35's sustained G capability is not sterling and I'm confident that the trainer's sustained G requirement exceeds the F-35's capability. But the trainer will also be used as a lead in to F-22 and other jets with higher aeroperformance than the F-35. However, the trainer also needs to be able to simulate the functionality of the F-35's cockpit and avionics in order to teach those cockpit and systems management skills. So its an aggressively complex program.
And if the cockpit and systems are done properly, the intent is not only to use the trainer to teach those skills to lead-in pilots, but to offload training sorties from the actual aircraft and use the trainer instead of the actual aircraft to keep those skills polished in current pilots. It'll be interesting to see if they are successful in making that happen. Especially since the F-35 software and systems will (supposedly) be constantly upgraded. How will they make sure the trainer software/systems keep up with the evolving aircraft it's supposed to represent?