I just wanted to post the following info, because I couldn't find satisfactory information when I tried to attach two 500gb HDs to my WL-HDD.
First off, cables:
1. A 44 pin 2.5" female connector to two 40 pin 3.5" female connectors, like this one: http://cablesonline.net/182dr44la40d.html
2. A 44 pin gender changer for the WL-HDD. I ordered it from the same company above, but upon opening the package I discovered it was simply a 44 pin pin-header you can buy at any electronics store for less than $1.
3. When you change the gender of the WL-HDD 2.5" connector, you need to mirror the cable described under 1. That means that you have to carefully pull out every top pin and every bottom pin and switch them around. If you don't do this, you'll just be connecting pin 1 from the WL-HDD to pin 2 of your HDs... It's a lot of work, but it's the only way to do it.
4. If you decide to attach two HDs, there is a specific order in which to connect the drives to the cable. Set one HD to Master and the other to Slave, and connect the Master drive to the center connector of the cable. The Slave drive must be connected to the end-connector. When attaching just one drive, set the drive to Single or Master and connect it to the connector at the end of the cable (if you have two connectors).
5. Last but not least, a suitable power supply for your drives. I used the power supply of a 3.5" USB enclosure that was rated 12V 2A and 5V 2A. A single hard drive will use approximately 5V 0.85A and 12V 0.5A, so you can easily run two drives off such a power supply, but forget about attaching the WL-HDD to the 5V, it uses too much power (approx. 7Watt @ 5V = 1.4A, and 1.8A peak). So either get a more powerful PSU, or keep your original WL-HDD PSU to power the WL-HDD.
I ended up putting everything into an empty PS2 case, added a 12V fan to run off the 5V of the HDs' power supply, and daisychained the HDs' PSU to the WL-HDD PSU so I could have one cable to the wall socket instead of two.
I have installed Oleg's firmware 184.108.40.206-7g, and partitioned the two drives (one drive 10gb/512mb/460gb, the other a single partition of 470gb) and all is running well, even hdparm works as expected and the whole kaboodle pulls 32Watts with both drives (Seagate 7200.10's) spinning and the WL-HDD after boot.
I hope this info will come in handy for someone. Good luck with your own projects!