Scotti, Just because you can see where the bridge was, does not mean that is where it's suppose to go. On well made violins, the inside point of the F hole at the center is suppose to be the makers refrence to where the bridge goes. On "Some" well known mandolin makers, the same thing applies, however, they all need to fine tuned. This, as you know, can be done by playing a note at the 12th fret and then playing it open. If the 12th fret note is higher or sharper than the open note, then the bridge is too close to the fingerboard and must be pulled back towards the tailpiece a little. This is repeated with a retune after each incident until the instrument is in tune.
One of the primary reasons bridges are not glued is, as the instruments dries and shrinks, or expands here in Oregon, the inntonation will change some. If the bridge is glued down, how will that happen? Also the changing of strings in brand and guages will affect the inntonation too. Actually, years ago, I did glue down some bridges and as luck would have it, they reappeared at my shop not too many years ago, and sure enough, the position of the bridge was wrong. Yep, I had to cut off, grind and do finish work on the tops. Sucked!.... Don't glue the bridge.
Cartwright's Music & Repair Shop
"I repair what others sell"