Any hints on how to limit WAL file disk usage?

I have an embedded application where we use PostgreSQL to store
configuration data. For the past few years, we were on a 6.x system,
and are finally trying to update to 7.1.2. One of the issues I face is
that the WAL files occupy a pretty significant amount of disk space. We
have figured out how to reduce the size of the files (we are using 500K,
and it seems to be OK), but whats not clear is how we can limit the
number of files to some maximum value (say 3 or 4). The configuration
variables seem to provide a guideline for this, but I have seen the
actual number of files exceed these many times. We don't do large
updates/inserts as a rule, and for this application it would be better
to wait while the files are committed rather than overrun the maximum
number. The filesystems are all memory based, and we have a hard limit.

Anyone have any pointers? I've done some cursory examination of the
code, but was hoping I might get some pointers to speed my progress.

TIA,

Bob Crowe

RCrowe(at)stbernard(dot)com