Mine seems to favor the 8.8/8.75. It will peek this prop at about 19.3 to 19.5 on the ground. This is on 15% nitro. I don't know what it will do on FAI fuel. The head shim I use is .005. The engine comes new with about .012 to .015 total. The thicker shims should be used until the engine has had a few ground runs and flights with a prop that will allow the engine to get up past 20k on the ground. As Johnson said don't let it run wide open on the ground for more than 5 seconds. I don't even like 5 seconds. It will fall of the pipe and then take 200 or 300 ft after launch to get back on the pipe then a lap to unload. And then still not go very fast. You will have to get the best needle in the air. After I've got the needle set I start the engine at 2/3 throttle and leave it there until 5 seconds before launch. It's generally getting on the pipe just when my caller is turning it loose. When the needle is set right the motor is running at about 18.5 to 18.7 on the ground.
Mine doesn't blow Nelson plugs unless I get it too lean.

Denis