I just installed a 1TB drive in my WL-700gE and it works like a charm.
Since such large drives are difficult to come by in PATA, I ended up using an adapter (I used a "Sabrent IDE Ultra ATA-100/133 to Serial ATA (SATA) Port Mini Converter", http://www.tigerdirect.ca/applicatio...086&CatId=1455). I've had to cut some of the shielding to make room for the adapter, and it pushes the top-cover a bit, but all in all, it fits OK and it works just fine.
I used a WD10EACS drive because it's the lowest-consumption I could find, survives many more spin-up/spin-down than most 3.5 drives, and it also happens to be the quietest drive there is nowadays.