I have not seen the Jato on the track, but I have looked at the truck before it was released at a hobby show. It looks pretty cool, but I am not sure this would be the best vehicle to mod for speed.
How about going for a bigger engine rather than running 2 engines?
The only vehicles I have seen with twin engines are monster trucks such as the Giga Crusher.
http://www2.towerhobbies.com/cgi-bin...&I=LXHJB2&P=ML
My Losi LST has a .26 engine weighs 13 pounds and goes about 39 MPH.
I am sure you could get the 5 pound Jato to go much faster with a bigger engine, the only downside is that you would have to greatly mod the transmission, if not build your own.
Find the most powerful engine with the highest RPM.
The other problem with the Jato is that there is not much room for a bigger engine as far as I can see, I could be wrong here.
The truck seems pretty balanced also, however, the engine is mounted to the left side of the truck.