I wouldn't cram many extra drives into a G4 case. Most of them have 208W - 237W power supplys if I remember right. Not to mention the cooling issues.
Get a PCI expansion board and a atx case.
PCI Expansion chassis aren't that expensive anymore. I bought a bare 7 slot board w/ interface cards and cable, and a full tower server case w/ 400 watt power supply for under 1,000. That was over a year ago. I run 6 ATA and 4 UW SCSI hard drives on that board; never had any really issues with it. (Magma expansion chassis don't work with pre 10.1 versions of OSX though.)
A cheap PC case and a 3 slot board would cost around 500 dollars if I'm guessing right.
*note : if you get a 7 slot board, they are actually 8 slots total (one for the host card) Unless you fork over for a nonstandard case, you'll have to get creative with some metal cutting tools.
Also be warned..I seem to recall reading about lots of individuals having problems getting optical drives working properly on most PCI ATA cards. At least I'm pretty sure that the sonnet and acard ATA cards can't (specs on the website state as such) never tried it myself.
It is possible to get fairly long round ATA cables. You could purchase a 5 inch external drive case. No idea on vendor, but I thought Kensington had them. Running A ATA outside of your case though may not be terribly reliable or convenient, but it would work
[ 04-01-2002: Message edited by: Nicholas Savage ]