I think 5 gallons of pale ale and 10 gallons of IIPA, go for a big difference. Same grist composition, mill setting, length of mash, etc. The runoff speed is an interesting variable, do you run off at the same volume per time, or go for the same time for run off?
As for your match experiment, I doubt it will work. It depends on how you do it, but keep in mind that there needs to be about 13%+ O2 in the air you're testing to maintain a flame. I don't think anyone is saying that CO2 blankets are complete BS, there is some effect, especially if there isn't a lot of air currents. But it's not rock solid like some people seem to think, and it will dissipate over time, if not from air currents then from diffusion. If this didn't happen you'd suffocate in Death Valley.