Your ideas of a skill competion would be a fun part of club get together, and one I hadn't thought of.

I was more focused on actual airsoft tank battles. I guess 6mm paintballs could work, but you would have to wipe down the tank after each battle. The flag approach was another option, for those who didn't want to buy paintballs.

I'll try building some tank target flags, and see if I can come up with something that makes them hold fast but not so strong that they can't be knocked down by a 20 ft airsoft hit.