Yes, it is almost impossible to control all the variables as you mentioned. That and I only took 3 shots each, which isn't a big pool of data. It was my fault for not bringing more potatos. Plus it takes a long time to measure each set of shots.

Hairspray is great but results in too much gunk. I have had success with insect repellant. I did a fuel test on several different fuels to see how each would perform in my gun. This is the result of that testing:

[youtube][/youtube]

I made some potato arrows to shoot out of my 2'' pneumatic cannon. Got 20% more distance and shot super straight. Fun to watch in the air. The tutorial is on youtube.

[youtube][/youtube]

And here is a screengrab of the arrow: