Re: Duncan doesn't fit
The chassis and overall dimensions of an F-spaced are the same as a normal spaced pups - it's simply wider spaced pole pieces.
I'd use a file and work it slow. A dremel is an appealing tool given it cuts the work time down, but you could easily remove too much material or even begin to melt the pickguard. As for the holes not lining up perfectly, you should still be able to use the holes... but you may not be able to raise the pup as high as you'd like. It also depends on how far off the holes are.