I have 2 sets. ( thats why I got the weights as fast as I did! )

Properly geared my RC10 gets about 38mph running Proline holeshots, and only 34 mph, running the Masher 2k's. Now, that is PROPERLY GEARED. If you don't increase your drive ratio when switching to the much larger tires, you increase the strain on the motor, by doubling it's torque demand, without benefit of additional gear reduction. The result is sluggish acceleration, shorter run times, and higher operating temps, which will result in reduced engine life.

As for the tire ballooning, it is entirely reverse of what you'd think. When you reduce the contact patch of the tire ( by ballooning), you increase it's tendency to slip under acceleration. The resulting loss of traction, will cause a loss of top speed, and a loss of control. To control ballooning, we tape the insides of the tire with heavy duty straping tape. It works for a few races, but the centrifigul force causes the adhesive to give, and the tape fails. If you want a true measurement of top speed, you need to run a tire that is immune to the balloning affect, namely a solid rubber, or solid foam rubber tire.