Putting /tmp on a separate volume?

[Oliver Iberien]

I followed the automatic suggestions for slices at install time and now have 
a /tmp folder of 500M. This fills up at odd times and I was hoping to install 
a second drive and mount a section of it as /tmp.

So far I managed to get a second drive partitioned. I replaced the slice 
in /etc/fstab for /tmp with one of the new partitions (in this case, ad1s1c).
KDE would not start because it did not have the permissions for /tmp any more, 
so I put the following entries in /etc/devfs.conf:

own    /dev/ad1s1c     root:wheel
perm   /dev/ad1s1c     0777
own    /tmp            root:wheel
perm   /tmp            0777

That didn't work. I initially tried with 0666 but that failed as well. The 
0777 did not seem like a good long-term solution anyway.

So... Is what I am doing possible? And what is the intelligent way to go about 
it?

Thanks,

Oliver