Over the last week I did a little informal testing
on cratering/fisheyeing. I posted the particulars in
rec.boats.building. The bottom line, I think, is
that certain epoxies, the more expensive brands,
just don't crater. They have additives to help
prevent it. The less expensive, less-modified,
thinner, epoxies do crater in some situations.

By the way, one epoxy I tested that didn't crater
was System 3 Clear Coat, which is a VERY thin,
non-blushing epoxy. I used it exclusively for
glassing my stripper kayak. I highly recommend it.
I tried RAKA, (and WEST), after my boat was 90%
completed, and I had run out of System 3 stuff.

I think I have learned the hard way that you get
what you pay for.