it wouldnt effect it at all if it was a little large for the maxamps packs, so if he were to make one it would best to make it fit the larger packs(like true rcs)
As for pack trays, I agree they should be big enough to fit the average high voltage lipo packs, 52mm x 165mm x 24mm ??? a taller pack could just set higher out of the tray, shorter packs could set on foam.
If I could only draw what I see in my head, then afford to build it, and finaly get to play with it...