I use mega/picco engines and find the best plugs are the picco/mega plugs.
I usually stick to no.6 but will use a no.7 if ambient temps rise.

Pip

Run the picco plug PT6C its a medium/hot plug with a cold body. The best place to get them is rcmart. They are about $8 ea. Everywhere else they want $12-15 ea. They last alot longer then odonnel. But guys do run the 77T O Donnell plug with good success.

Shawn.

definitely choose what ever brand of turbo plug suits the engine . But when it comes to the hotness / coldness , to be very honest it depends on a lot of factor when your racing , then just saying use this or use that.
Few thing to consider are
a) what nitro % will you be using .
b) shim under the head bottom also to be considered
c) what type of weather your in .
d) run time .
e) performance , torque v/s top speed in relation to engine temp you wish to run .
All the above should be considered when you have got your race face on.
regards
Alex

hands down the best bang for your buck.

RB R3 i think is the best money value even now....