The 18-8 seems the best. I get 7400 with a stock C-H 32 but with a 1/2" Walbro carb on it. I have another 32 that Terry at C-H modified. It turns the 18-8 at 7600. It also has a 1/2" carb. They both look like they were designed to be model engines from the beginning. I have the Abbell mufflers on them held on with the original spring retainers.

Jim