I had the same fitment issue with the screws....just a little tight is all...just screwed it down...made things tighter actually.
Ive never found the 483 to be unstable at speed...just slow speed...this one just adds speed like the others without as much twitching in chop...I know some folks call this 'loose' and like it...but with our inland frontal garbage winds overhead this translates into nasty twitching below the water....
No experience with the 633 as its out of my quiver....
Thanks a99 - your post motivated me to try this
As far as 450 - all of this started because I was looking to get rid of the high foot pressure of the 633/483, moved into the 683 and took care of that and wanted more speed. When I added the 450 it felt like the 633/483 all over again.....if I were you I would try the 483...its very very nice. Then try the 425 later if and when you want more speed....all this is subjective, Im just feeling comfortable with the 425, maybe heavier riders appreciate the 450 I dont know. I was actually thinking about sanding down the 483 to just make it thinner but didnt want to screw it up totally as its still a great stab (just chewed up to hell on the tips)
Its been frustrating buying all of these stabs but its given me something to look forward to during the COVI bullsh8t...