PG block sizes

Hi, All

I'm trying to tune a software RAID 0 (striped) on a solaris 9, sparc box.  Currently I'm using a raid 1 (mirrored)
arrayon two discs for the data area, 
and I put in 4 new drives last night (all are f-cal).  On the new array I have a width of 4, and used the default
interleavefactor of 32k.  I believe 
a smaller interleave factor may get me better read performance (I'm seeing a bulk load performance increase of about
35%but a 7-8x worse read performance 
between the two RAID setups.)

Conventional wisdom is  using an interleave factor < = db default block size gives the best read performance.  I would
liketo try that (though this testing 
is burning a lot of daylight, since I'll have to reload the db every time I remake the RAID.)

Question:  what't the best block size to use for postgresql on solaris?  (I'm using 7.4.5)