Hi,
Just read where Cook's Illustrated had experimented on how to prolong tomato storage. They began with tomatoes stem up or stem down for a week. After a week, stem down was in perfect condition and stem up had shrinkage and beginnings of mold.
Estimating the wound where the stem is allows moisture to transfer out and mold/bacteria in. They conducted a second experiment with tomato stem down and another stem up with tape over the stem. After a week, they were both in good condition.
(I'll add to this later, there is a thunderstorm rolling in)
Regards,