When magnet cars are run without traction magnets the magnets are usually replaced with brass weights and the track voltage is reduced to 12 volts or so. When I built a couple of Tyco cars with brass weights I found that they ran better at 11 volts.
The Mega G has very small traction magnets, so brass weights that fit the magnet pockets might not be heavy enough. Some tungsten putty might be a better bet.
I want to try simply raising the mags a bit & see if I can find a sweet spot. I agree though, taht you have to turn them down or it's like trying to control lightning.
first try, stock with magnets removed, no weight added
Very jumpy till I trued the rear tires, then not to bad at 15 volts had to be be slow on the power or the rear tires would spin. Looks the real speed, gets up and going on the straights and slow it down for the turns. 10 second lap times, run 100 laps.