Initial fitting took something like 45 minutes for me, as I went VERY slow, using a honing block and oil.
All you do in this process is file a small 'stub' off of the mounting lug until it JUST fits into the frame. My advice is to give it a few light filing strokes, wipe it off and try to fit... lather rinse and repeat.
You will be surprised when it finally fits into the frame... it happens suddenly, so you want to be sure not to take off too much - take your time.
Anyhow, following some problems with cycling using the cheap Federal ammo during my first 500 rounds of so, the gun now operates flawlessly with all ammo. I believe the conversion needed to be broken in and I also believe that the .22 kit needs good lubrication to operate correctly due to the low relative blowback force of the .22 round.
Operation has been flawless from day one using higher-powered .22 ammo - it was the cheap Wal-Mart bulk Federal that gave me problems originally.
I haven't done bench rest testing yet, but this is a very accurate piece.