planning on upgrading my son's radio to either a 3PM or Airtronics (comparable price, of course) running 2.4ghz. Any suggestions? Also, which high torque servos should I get for the steering and throttle? Can I mix Airtronics or Sanwa servos if I buy the Futaba radio? thanks.

Why do you want to update your son's radio? Is he going to race? Do you need a Pro radio? How old is he?

I have a 12 years old son that races, he tried the M11 and it was to heavy for a long main, so decided for the Spectrum DX3R.

Servosur are going to get a lot of advices all good I supposed. Again, if you are running Lipo, look into ACE servos, they are fast, powerfull and so far no problem. (ACE and Associate are the same servo).

Mixing servos is fine. Just make sure they are plugged into the receiver correctly, black/red/other in the correct order. Well, some aren't exactly that, Spektrum servos for example, but the darkest hue for black.

Not the issue it used to be, plugs are standardized now. Back in the day you sometimes had to change the order of the wires in the connectors with some combos. Now it's just making sure the plug isn't in backwards.