I missed Page 2. My bad.
I have not messed with cams at all because Nakaru is the only one I saw. They are China crap so I never bothered.
The best thing I found was to use the OEM cylinder head. It has a smaller combustion chamber, thus higher compression ratio than the heads supplied with the 80 or 90 cc kits.
I'd go with the 50mm kit. It's a much bigger difference over stock. They wind up near 90cc's, and have a lot more torque than the 80cc kits.
Also use a 24mm carb, and get a bunch of jets. I wound up at 42/110 w/ the 50mm kit