Changing FS when full

Hi,

I have a big database on FS1, now almost full. Have space on FS2,
where I created a tablespace and moved every table and index to it.
Still, lots of space used on FS1. The problem is not pg_xlog, but
base:

# du -hs base/105658651/* | fgrep G
1,0G    base/105658651/106377323
1,0G    base/105658651/106377323.1
1,0G    base/105658651/106377323.2
1,0G    base/105658651/106377323.3
1,0G    base/105658651/106377323.4
1,0G    base/105658651/125520217
1,0G    base/105658651/127352052
1,0G    base/105658651/127352052.1
1,0G    base/105658651/127352052.2
1,0G    base/105658651/127352052.3
1,0G    base/105658651/127352052.4
1,0G    base/105658651/127352052.5

Unfortunately no volume management is available, so I can't move
disks from FS2 to FS1.

I could play soft links tricks, but I'm afraid of paying the
FS-traversal penalty on each file access (is that right?).

So, any way of instructing PG (8.1 if that matters) to place those
files elsewhere without an initdb?

Thanks!

Fernando.