The 2 cell limit is the problem. These cars can easily run 10 minutes if 3s were allowed in 4x4. These cars are closer to 8th scale than they are 1/10th scale so the 2s limit is really on the edge in terms of the battery power.
We normally don't run much longer than 6 or 8 minute mains. I could barely make an 8 minute main with a 2s 5300 Thunder Power g6 pack. I doubt I would make a 10 minute main.
The 4x4 SCTs are popular with 8th scale guys locally. A lot of them would run 10 minute mains if given the choice, but the 2s rule prevents it as most probably couldn't finish the main on larger 1/8th scale tracks.
3s with 2400-3000kv motors would be perfect for 4x4 scte. We could easily make 10 minutes running 3s 5000 packs in our Losi 810s.