[Efroeh]

If the gears in your axles are metal I'd try and add some weight. Tires if they sack out always could add some spray foam to make them harder and able to take the weight. For adding ballast you have lots of room to add lead even fill tires with bb's then fill with foam add weight and make tires more rigid. I wouldn't give up as I could see with a few more tinker time on the bench it will work great. If not pm I'll take it off of your hands