XRAY - Model racing cars

i am using a monster stock quad mag with a 21/84. i have been told to gear low as it is a quad mag.which gear would be most suitable for a carpet track which is fairly large with mixed corners?

It's hard to tell without obviously being at the track from your description i would say start off about 81/26 and play around the gearing, start off low and work your way up

At your track....pick the longest straight and gear to achieve max speed 3/4 down the main straight to start off with.
If your track has a large infield where time can be gained if you drive well, go a little higher to get more torque.

It really depends on the track you run but the above should be a good indicator of where to start.

S