On the MGM the problem with the brakes was that when you were coasting the brakes would apply for a second. Making jumps slowing down interesting. You would have to hold the throttle in the air. I think you just need to program a different reverse type.

One thing I noticed when I went from the MM to the Quark was that I had to gear down because of the fact that more juice is getting through. That may be why it feels sluggish and you may be in fact thermaling when you nail the throttle. I hate to say it beacuse I know your at 9/46 and it gets harder to gear down any more, but there are a few gearing options left. Another option is a lower kv motor. The 7xl is a hot motor for a big truck. You don't need speed motor you need a torque motor!