Help with tailpiece

[Thurber Mingus]

I bought my son a MK F-style mandolin (used), and when I got it I noticed the tailpiece was pulled forward by the string tension, and the lower (of 3) screws was missing. No problem...got another screw mailed to me, found that 2 of the 3 holes are stripped! After taking the tailpiece off, I see there are 2(!) sets of holes for each little screw, and the lower screws two holes "overlap", so there's no way it will engage the threads.
My question...how to fix it so as to get the tailpiece back on. It's a beginner's mando, could I move the tailpiece down a bit and drill new holes, or is there a limit to how low the piece can "sit" on the body? Do the strings normally contact the tailpiece closest to the bridge?
It seems the body is too thin to drill and dowel the old holes, so if the above would work it would be easiest (and cheapest!), as I can do it myself.
Please advise!!

[sunburst]

You need to dowel the holes. The "standard" quickie repair is to glue tooth picks in the holes and re-install the screws. With the extra and overlaping screw holes that you have, it would probably be better to do a little more of a "real" repair by gluing in small dowels that fit the holes pretty tight and re-drilling for the screws. I don't think you really need to drill out the holes before doweling, just get small dowels that fit the existing holes pretty tight.

[Bill Snyder]

...It seems the body is too thin to drill and dowel the old holes, ....

There is a tailblock under the ribs. It isn't real big, but it is big enough to do as John says. Also you will be less likely to re-strip the holes by predrilling as John mentioned and don't torque down on the little screws with too much pressure.