Rod,
Thanks.  I'll do that.  MEK is a vehicle in the PR-1005-L material.
I took a little extra time in draining at various angles to avoid any puddling at the mid-rib or the root.,  The fuel outlet opening is very close to the bottom of the tank.
I don't know what original sealant was used by the original builder... about 20 years ago.
I made some small sample pours into a plastic container, and tried various solutions with MEK, after observing the curing of the unadulterated material.  No apparent problems other than those I already mentioned.

Terrence
L235/320 N211AL
89 enjoyable hrs.
 incl.  x-c IL to CO, visiting friends, and some $100 burger hops.