I'm not too sure why people are still doing the drip acclimation - I've had 30+ rays that I've just scooped and dumped and never lost a single one due to that. If you're getting your rays locally, your water is already probably almost identical - no point in acclimating. If your rays are coming from any distance, the water in the bag IS dirty, so get them out of the dirty water ASAP - scoop and dump!
I agree with Nic on the tank - if you can go 5x5, I haven't looked into prices but I'd think a 6x4, 8x3, or 8x4 would be comparably priced.