with 15psi and 91 fuel im guessing anythnig would knock ever more so if not intercooled well enough, high comp pistons spool turbos nicely, especially with a large overlap cam, but arnt as efficient as a high lift low overlap cam, 11:1 should work fine in a 700xx running on 98 fuel, just adjust ignition maps to suit, it just depends on how much boost you want and what kind of riding your going to do
My boss at AMS was an engineer and had a ton of turbo experience. He worked closely with precision turbo designing turbos for our cars. Fast spooling and made tons of power. One of the guys I worked with in fabrication was building a turbine for NIU while getting his degree in mechanical engineering. He used a really small turbo for it that probably would have worked out awesome for the xx. I would get Precision Turbo on the phone and explain to them your situation. I think based on a few questions they could help you narrow down to the proper turbo.
Check out the Raptor forums, a lot of those guys are already running turbo setups. I called English Racing when I was thinking about a turbo setup and they said they could do it, I didn’t really get into to much detail with them over the phone (didn’t know what I wanted to do yet and didn’t want to waste their time) Here’s a link to turbo talk on one of the Raptor forums, I think they will have a lot of useful info that may be able to be applied to the XX.
No joke, I just paid $220 for 20 gallons of C12
