mercury: these are no discharge trays, they're *equalizing* trays. You're supposed to dump your packs at high amp (20 or 30A) whan you're done running and THEN equalize them (at low current). You're not supposed to throw your packs on the equalizing trays when there's still 1000mAh in them. I mean, you can, but it's not their purpose.
However, if you do, because you probably don't own a discharger, using 5A will just be quicker than 2.5A... That's pretty much it. Problem with 5A is that it heats up a lot more, and this is why the RS has an average reputation when it comes to dumping full packs... That's just not what these trays are designed for.
Their real use is to EQUALIZE packs. not discharge ("dump") them.
Evecerator: other question. Assume I want to deadshort... My discharger (RS) only cuts at .1V / cell. Will I blow up the whole block if I hook up together the pack's + and - when there's still 0.6V in it? I don't feel like buying another discharge tray