I have an archtop guitar with a floating bridge. I've been told that it's important for the bridge to have maximum contact with the face of the guitar, but I'm seeing a gap between the bridge and the guitar. I'm pretty handy with my hands and I'm wondering if this might be something I can take care of on my own. What do I need to do to correct this problem?
Be exactly sure where the bridge needs to go for intonation. Maybe put some masking tape or suchlike that will not leave a deposit on the guitar, partly to protect the area, and partly to show where to put the sandpaper, sand side up. Then rub the bridge 5 or 6 mm across it. That way, the profile of the bridge bottom will get to match that of the belly at the right place.
What grade paper? it depends on the material of the bridge, how much you want off, but as a guess, if 180 is too coarse, start with 240 and go to 320 to finish. Check the gap often!