Well the gears seem to be holding up for now, I ran another tank yesterday. I got even more power out of it since it was warmer, like 50 degrees. I was able to ride wheelies down the whole driveway lol. Got it up on two wheels and used the rear bumper as a wheelie bar lol, just hafta blip the throttle to keep the wheels up.
I think for an RTR engine the 4.1 has the perfect amount of power. It has a very controllable amount of power. It gives wheelies when you want, but you have to try to wheelie most of the time. You don't need much throttle control to be OK with this engine. When I had a Wasp .28 in my old savage, that required some control, but the 4.1 is much more easy to drive with.
The plastic roll cage so far has been VERY helpful. I've flipped the truck over many times while doing wheelies and I still have not a scratch on the engine. By the looks of it, its not gonna do much good on upside down landings and stuff, but its been helpful for preventing scratches on the engine.
I replaced the spring for the breaks with some fuel tubing and that help the breaks, but they still suck, and I am pretty sure its mainly to do with the weak servo.