Dave used to come out to shows here in Michigan pretty regularly, though it's been a few years since I've seen him at this point. Very nice guy, and yes he's a mailman (maybe retired by now).
They didn't ask him to jam, so to speak, but for a master - he had been recording already since the late 80s from what I can tell. The LP on AMT was originally supposed to be a 7" on Stomach Ache in the 90s if I remember right.
He's got another tape on the Square D label called All Washed Up, but I haven'the been able to find that or anything else. I used to bug him about finding his old masters, but to no avail.