The Fox is a surprising agile 2WD off roader. I've had my runner on ALL surfaces & even a proper track. Always puts a big smile on my face! On loose stuff the back end wants to do its own thing, But if you have the standard oval block tyres on that's the reason. Pin spikes are better, But don't last long. Try getting some of those aftermarket ones that look the same. I think CRP did them.
I do love the Fox though, Just because I had soo much fun with one when I was younger. The only drawbacks are the radio box that's a pain to get into & those rear arms break easy. Shame the gold plating just drops off the wheels too as they look well smart!! If you've never owned one now is the time. Cheap examples are going on ebay right now.