The replacement OWC Mercury Legacy Pro that I received doesn't work reliably on my MacPro11,2 or PowerMac7,2 or PowerBook5,9. It will unexpected eject after short periods or lock up. It would only appear on the PowerBook after reformatting it on the MacPro (APM & Extended/Journaled).
My PowerBook5,9 will consistently boot from its old ATA internal drive and the external FW800 back-up drive.
I looked at KingSpec but they didn't have a large capacity drive. It's more convenient for me to keep the internal DL superdrive than replace it with a 2nd internal hd. I think I'll be returning these and give a Crucial mSATA SSD + adapter a go.
I saw that someone was running a PowerBook5,9 with a single 2GB SODIMM stick installed, although specs say it will only take 1GB sticks. The 5,9 can use the faster PC2-4200 ram which is available in 2GB capacity. After I sort out the SSD situation, I might try 2x2GB.