Water Leaking In The Trunk!

There is a VERY high chance it is rusted out along the bottom of the window seal lip since dirt, leaves and other crap gets in there and can only be cleaned out if the trim is removed.
That junk holds the moisture.
I actually thought about and still may, make a drain down in that channel that goes into the trunk then across and out the bottom of the trunk on one side.

One other thing that leaks on vinyl top cars is the little screw end that protrude into the trunk from the trim across the back.