My question to
>you all is, would changing back to regular GL-4 make a difference once a
>little leak starts

I believe that the reason synthetics occasionally cause leaks in older
vehicles is that the synthetic oil causes the rubber seals to swell less
than conventional oil. (all rubber, even "oil resistant" rubber swells
somewhat when immersed in oil).  Anyway, when switching to synthetic, if the
seals are old and slightly worn already the loss of swell shrinks the seal
and can cause a leak.  Though I have no direct experience with going back to
conventional oil, I would think it would swell the seals up again, possibly
allowing them to seal.  If you are desperate and daring you could add one of
those seal-repair-in-a-bottle additives.  Basically, they consist of
solvents that will swell the rubber seals more than oil itself.  This can
slightly enlarge the seal (and soften it) which may allow it to re-seal.
The downside is that these solvents can also degrade the rubber in the long
run so you may have the problem return sooner than you thought.
Mark