Today i ventured to try the schematic for a hardrive on my slim ps2. So far so good. The wiring wasn't too bad (I've soldered 5 days a week for 3 years). Finished it in about one hour and fifty two minutes :). Pictures will be uploaded soon on my handywork.
UPDATE: Cut out the back and stuck the wire's through. All i need to do now i find a small power supply for the hardrive.