I will! lol - Took it out earlier...it ran away!? :S Was on spektrum so should've kicked in. Faulty ESC i'm thinking.
Anyway, tbh Simon, i think the 80A will be just fine in your 3906 - It's a bit smaller than the 3905 hence a bit lighter, and on LiPO power, i don't think it'll struggle much (if at all). Still, it's prone to getting hot and underperforming, so i'll quote Guns for you: "Buy expensive, buy once".