Is 50mm medusa no use??!

I accidentally bought the 50mm can version to go in a truggy which I now realise is too small can for 1/8th (running 5 s)
Am I right in thinking the only difference in 2200 70 or 80mm is the can length resulting in better cooling?
If so then I will have to sell the 50mm as I can't see what I can use it for.

Also have a Mega Motor 1700kv, again with approx 50mm can, same rules apply I guess?