Looks like you didn't miss anything Gary - only rules so far are:
"Each entry will be in an individual thread, titled: Hand Gonne Contest - 2011 (instert name/title here).
Minimum components will be: plans, pix of building it, and pix of firing it.
All board rules of safety and legality apply."
So yes, all scales are competing against each other. Personally, I view it as more of a challenge than a competition. I've never built a barrel before, so I don't care if I win - just if I meet my expectations - which are kind of high.