Hehe, I was thinking the same over lunch. Just because the stage is expanded in anyway to "increase" chances, is only equivalent to splitting a dollar into two 50 cent coins. The fraction of the result will equal the same.
that's not true . the number of items rendered is proprotional to the concentration of sandbags x the concentration of attacks .
I = c[X][A]
I = items , c = constant , X = sandbags , A = attacks , [] = concentration
if you split the sandbags into 2 groups , you halve their concentration . if you split the players into 2 groups , you halve the concentration of attacks .
I' = c[X]'[A]' = c([X]/2)([A]/2) = 1/4 c[X][A] = I/4
by doubling the size of the stage , you cut the yield down to 25% .