Before installation, I saw a great many people say that the Kadet II kit required very little fitting. A few strokes here, a few strokes there, and it's good to go. I can only assume that these testimonies were only for the older-style of Kadet IIs because my experience was certainly not like that. To get the long front rail to fit in my SP-01 suppressor ready, I had to do a lot of filing. I couldn't tell you how many, but hundreds of one-way strokes per side with a metal file I picked up at Ace Hardware. I only filed the sides of the rails, not the tops or bottoms. There were points at which I felt discouraged and worried about over-filing. Granted, I did over-file the lower half of the right rail by a little bit (the railed ended up slightly slanted), but the left rail is perfect and the top half of the right rail is too.
Afterwards, there were metal shavings everywhere. I'm still concerned about shavings in the nooks and crannies of the slide that could cause wear. But, on the bright side, it slides in just a hair more snugly than the 9mm slide, so the final product is good. I am excited to shoot my Kadet on the cheap now that I've sold most of my 9mm for the going market rate.
Just wanted to share this in case anyone was looking for an experience fitting the new-style, long-rail Kadet II kit. Don't be discouraged! YMMV