Sorry for taking so long to parse your mail and get back to you.

The problem had been some of what you mentioned, but mostly that no
matter what I do, I need to use a full set of modem lines to a terminal
for the tty process to reliably work, no matter what I put in ttys,
and no matter what is set in the prom (which should, in fact, be the
overriding guide to how the lines should parse)....

I only found this all out because I needed to make an AIX PowerPC headless
the other day, and it has *no* way of being headless w/o a full serial
line set, so I grumbled and pulled a real tty line out of storage and used
it, whereupon I decided it was time to see what the scoop about the IPC
and NetBSD really was.

It all sorta sounds a bit like a bug to me, but it's not that big of a bug.

-matt