[BrianG]

Didn't read the whole thread, so this might have already been mentioned, but if you need a longer tray, simply cut one in half and spread them apart. Chances are you only need no more than 1", and a gap that big is no big deal.

And instead of cutting out a notch for the wires (which weakens the tray), consider putting in a dense foam spacer in the big enough to allow room for the wires to exit.