Most of that I covered in your other thread, but I'm getting a 9.5gpp arrow (29.5" 450 X10 with 120 gn point) off my medium 42lb CV9 at 214fps. My draw length (measured to the grip + 1.75" is 29")
Groupings are how well you tune them. I love the feel; smooth and easy through the clicker- just ordered a second set and I'm booked to go to the World Masters in Japan next year and confident enough to be taking them with me there.
You can have a slightly higher BH than the 7.5s. The draw loads early, but the last 5" are almost effortless. You'll think they're broken, because they go light. They don't have let off but it feels like it (Border did make some recurves with let off but decided that for now, it was a thing for compounds!) but you get used to it pretty quickly and it's a great way to focus on gold, knowing it's a tiny effortless squeeze through the clicker, even the last arrow of the day. Sorry to wax lyrical. But I do like them, and will be shooting two sets soon.