New discovery!! I just noticed that my drop in brass 3:1 gear boxes from Mato for the HL Panther G have axles thta are just a bit too short which results in the tracks rubbing on the molded supension detail on the hull. I think a washer ground into a D shape and inserted into the drive sprocket should do the trick although I may need to get slightly longer allen screws with which to fasten the drive sprockets.