I obviously have no more experience with timing belt than you do, but I figured if you haven't seen
this whitepaper by 234, you may find it useful.
234 and 612 both said in that thread they successfully used 15mm belts without problems, with 5mm pitch. .2 pitch is about the same so that makes sense.
I really like the sliding tensioners that also help the belt engage the sprocket. If it works as planned it should save a lot of weight over chain that way.
I'm sure you know but Gates has in the past given teams offers for free drive belts in the KoP. I think they allow teams to get some specific kinds, so it would make sense to model around those particular sizes to save money.