"...then smaller amounts give the head a boost every time..."
Seriously tho.. if i was gonna build boost bottles i might use a sphere. It would look cool and no matter where you stick it you could just orient it with the nozzle at the bottom. Finding a source of these different volume metal (?) spheres might be difficult but i'd find it and keep it a secret..
A 6" long X 1.25 " diameter tube (half of a paper towel tube) has near the same volume as 2.25 diameter sphere (a billiard ball).
I think the billiard ball is easier to fit than is finding a place to put the 6" tube vertically.