@JohnBartholomew
Your idea about a tmpfs mount is also not that hard and you can be more sure that it's actually consuming RAM, right? (see Chris Dodd's comment at Nick's answer)
mount -t tmpfs none /new/path/for/temp -o size=32m
dd if=/dev/zero of=/new/path/for/temp/zero.txt bs=32m count=1
Probably dd will complain that there is no space left on the device. Also, I don't know how much RAM will be used exactly, but if you're talking about MB's than this should be fine.
