This is gonna seem like a stupid question, and I'm 99% sure I know the answer but I figure why not ask the council before getting stuck with something I won't be able to use? The scale length of the current board is 25.5" and 21 frets, which drives me crazy to no end; so I figure buy a used MM neck with the same scale and 22 frets and voila! Instant somewhat-sanity.
Since they're both the same scale length and such, my thought is that nothing will be moved or shifted which should mean intonation won't need to be redone but technically you're adding that 22nd fret so am I right in assuming will be OK, or will it actually not work for some obscure BS reason?
do you have pics of both because I could give a way better guess that way