I had a mandolin that I repaired, and the bridge does not fit the top at all.
I have done bridge fitting on many mandolins as long as it is not way too far off using the proper method (shown in FRETS.COM).
The last one is really hard to fit, after sanding for 20 mins, I gave up, there are still gaps between the bridge and the top.
I came up with an idea: use epoxy to fill in the gap. Here is what I did:
1) lay piece of plastic sheet between the bridge and the top
2) put on blue tapes on both sides of the bridge
3) spread thick layer of epoxy under the bridge, then lay the bridge on plastic sheet (i.e. on the top sound board where it's supposed to be)
4) tune the strings
Leave it overnight, the next day, I take out bridge again, remove the plastic sheet, the blue tapes and sand off some expoxy residue on both sides of the bridge (then put it back on , etc...).
It was worth a try for me as the worst case, I only need to buy a new bridge and redo, but it works well so far (for the last two months).
I am wondering if this is a good method or a crazy method to avoid.