I just checked with the bare battery tray. They fit with plenty of room side-to-side. On the length, it looks like one of the wires will hit the tray. It shouldn't be a big problem to trim the backside of the tray to give the wiring some room. I measured the 6S battery with some calipers, and I came up with 40.5mm x 44.5mm x 137.5mm, but of course the way the wiring exits the shrink, the length is a bit longer where the wiring is located. You could turn the battery on its side so that the wiring wouldn't be a problem, but I don't know if it would be too tall.