First off: Good job!
I ran these CP pistons for years in my CX engines. I often took them beyond 11,000 and never had a problem. Take a good look at the wrist pin bores and the pins themselves. I changed pins a number of times because they did not seem to oil well. CP and I had a few brainstorming sessions about pin lube issues (on other engines as well). I started putting the pins in with Lucas zinc-additive oil to buy a little more time. I think it helped, but your mileage may vary. I always wished for a row of parallel ridges across the bottom of the dome, but never got it (oil droppers for the top of the rod).
That said, look very carefully at the rod installation. The oil hole orientation is easy to get wrong and that will reduce oiling into the wrist pin on an affected cylinder. They run fine with a rod in backwards....until something goes wrong. It is very easy to get these in wrong because the only rod big end access is through a pair of (rough, nasty) holes that are knocked through the inner crankcase during manufacture (absolutely bizarre manufacturing process). As you already know, installation is done by feel through a sharp-edged hole and often includes some well-oiled blood (your own) inside the cases.
Pretty fast motors, all things considered, but really expensive to build heads that breath well. If you are really careful, you can cut the 500 valve seats to take CX650 valves. I had better luck with aftermarket valves and going down to 5.5mm stems (with appropriate bronze guides). I also ran shorter springs with about .25" tall isolators under them to let the oil flow reduce the rate of exhaust heat getting into the bottom of the exhaust springs. You may find your springs get too hot (and soft) at the end of a long pull. The ports are too low and too sharp and so the top of the exhaust port gets smoked pretty quick.
Watch for "pop out" pitting on the back slope of the cam lobes....that will tell you for sure if the exhaust valves are starting to float. Those pits may be pretty small, but if you find them....you are in trouble. The cams keep working fine, even after they pit, as long as you solve the float problem.
Like the previous post says, over-rev is ugly and uglier if you chop the throttle instead of powering into an upshift, or a brake, to pull the revs back. With the throttle shut at high rpm, there is not enough intake air for the compression to help slow down those pistons. I was taught to push into the rear brake (throttle still open) to capture an over-rev. Easy to do on a bike.
JimL
PS....almost forgot to mention. The shim stack behind the last gears on the shafts is a little tricky and can lead to missed shifts. We also had a shaft slide in the clutch side shaft bearing, which makes the bike want to stay in 4th gear. Just food for thought. If you are ever putting one of these engines (with the home-brew trans work) together....and one day you pull the clutch lever and hear a little pop (and suddenly have a little extra slack in the cable) your shim stack is wrong and the input shaft has slipped in the clutch side of case bearing.