What make/model is that 11T pinion you're using? I'm having a hard time finding 48P pinion gears that small. I see on the RPP website they have some Robinson Racing extra hard and wide 11T pinions with an aluminum collar (https://www.rpphobby.com/product_p/rrp1411.htm) but I'm unsure if the extra wide will fit the Capra. Does anyone know, or have any other suggestions? Also, you're saying that 10T and less tooth pinions won't mesh right, huh?
BTW, I'm probably using the same motor in my Capra as you, an HH Puller Pro Stubby 2700 kv.
https://www.rpphobby.com/product_p/tra6747.htm