the .25 i think would be in between the .21 and .28, might be a little easier to control then the .28 but give you more bottom then the .21, i dont think people are realistic with there fuel consumption numbers, i could get barely get around 10 mins on my grp tuned in race conditions, now if i was practicing it would easily get that 12-14 minute run time, im sure the people stating that they can get 10 mins out of a .28 are not going by racing run time, they are going off of what they get for run time when they time it in practice