[RC-Monster Mike]

The 1 piece tray has a spacer "built in", Patrick. The tray had no additional spacer - simpler and allows lower battery placement position.
I am having trouble understanding why it doesn't clear - I have the same exact tray on the same exact truck and it has plenty of clearance to avoid the spur gear - I actually used the MBX5T Prospec for the tray design to begin with(this was the 1st vehicle I actually tested it with for proper clearance). The battery tray should have 1.25" from the outside edge to the mud guard relief(.25" deep relief cut into the bottom of the battery tray), which is more than enough for any of the vehicles I have tried it on. Some vehicles have thicker mud guards or tall nuts that may impede clearance slightly, but I don't believe this is the case with the Mugen. The picture seems to tell the story here, but I can't help but wonder why. Maybe the tray was machined improperly(I am human after all), but this would seem unlikely. I will try to get a picture of my truck and psot it here to show the clearance that should be present. If the tray is positioned against the mud guard over its entire length, there should be over 1/8" of clearance from the spur. Either way, we will get you figured out. :)