06-03-2008,09:28 AM
2HDs are possible, as the Hardware recognizes both afaik.
You can give it a try with HDL on Master and Linux on slave.
I have 3rd PS2, which should get my "fully modded PS", including all maybe senceless mods like VGA-Mod, or SIO-EE-Cable. 
I'm searching till weeks now for a way to connect 2USB-HDDs to one IDE-Cable.
It should Auto-Hook it as Master, or Slave.
USB-Port 1 --> IDE/Primary-Master
USB-Port 2 --> IDE/Primary-Slave
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony BBA
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
MAX/Datel 32MB&64MB
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux