>Or is it already possible to specify a size for tmpfs partitions?
Yes, the "size" mount option. In my /etc/fstab I have the line
tmpfs /tmp tmpfs defaults,size=800M 0 0
This gives me a /tmp of 800M, on a machine with 288M RAM and 1.2GB of
swap. Otherwise a tmpfs filesystem is limited to half of RAM. Yes,
this means that if I put too much in /tmp the machine will start to
swap, but that's OK with me because the swap disk is different than the
disk I record to.