I mentioned earlier it'd be better to run a G12 because the arm is a much better match to the C can mags.The reason Swiss said its a bad choice is the same as I said earlier.It'll run hot because the arm is too much for the ceramic mags.You will see better performance for a longer time with a G12/15 arm (same winds)The reason Drag guys run 20's is they run them for less than a second at a time.The heat from the arm isnt a big issue,whereas in a track car it'll get hot enough to wipe the mags glaze the com and so on in a minute.
Everything in these little motors is a balancing act,go too hot of a arm for the rest of things and it'll run hot and fall on its face.If you're a gear head think of it like over camming a engine.If you put too big a cam in a mild motor it falls on its face and runs like crap.The 20 wind is too much for most c cans and thats pretty much why they went to G27s with the wind,it needs the cobalt mags to perform as it should.
I've run plenty of G 20's over the years and they always disappoint,I've even run G27 arms in my Int 15 strap cans (essentially a ultimate G 20)that have (at the time)the strongest ceramic mags out and after a lap it is always the same thing.They turn into dogs because of the heat.
Now if you already have a G 20,gear it right,set it up correctly(9-38) and dont hot lap it 20 mins at a time and it'll be fun.It's just a group12/15 motor will run as fast or faster with less problems over a longer period.
Now to open a bigger can of worms.........besides gearing you should be worried about your body.It's possibly the most important thing on a wing car these days.
Do you know what length chassis you have?Also what track are you planning to run on?