I purchased the 105 HP Zipper kit through Jay last summer. Jay was very easy to work with and answered all my questions.
Installing the kit was pretty straight forward for me. Granted I have many years of mechanical type work under my belt, but I think anyone with a bit of patience and common sense can install these kits.
Engine fired right up and ran nicely. I still have some carb or syncing issues that I can't seem to figure out. Also, my charging system went wacky just before putting everything away for the winter. Might just be the rectifier but haven't had a chance to trouble shoot it.

Anyone contemplating this kit, I can only give you postive replies as far as experience with Jay and Hal.