Daisy chaining is NOT a good idea, IMHO. Especially FW800 and FW400 together. It will drag your sustained data rate down & you will end up with dropped frames. To be honest with you, get a 2 port Express FW800 card, get another G-RAID2 & dump the FW400 drives from your chain (I guess you can use them for backup).
That "mybook" drive is a disaster waiting to happen, though. My shooter brought some varicam footage to the studio on a fairly new mybook and it wouldn't spin up. He said it happens all the time and to bare with him. After 25 minutes, he smacked it on the side & it spun up. I wouldn't trust that unit with my archives or anything else. It's a Western Digital drive, which is on my list of stuff to avoid at all costs (along with LaCie's & Maxtor's).
When life gives you dilemmas...make dilemmanade.