Welcome to the Forum Diablo
As Fuzzy said, the KADET Kit makes for a fantastic .22 Pistol
It's a proven fact; the KADET is as accurate as any dedicated .22 Target Pistol
Yes, they can be Ammo finicky
There are a few "Tweaks" that you can do to help improve most Cycling and FTF Issues .... see the KADET KLUB Stickies for those
As for fitting the KADET Upper to your Frame:
In most cases, a Nail File will do the job
BUT, in some cases, a more aggressive File or even a Dremmel is needed .... maybe 1% of the time
Trust us, it is all easily done at home .... so don't get frustrated
Follow the instructions in the OM / UM and you're Golden