Yes, the less fleathers you got back there the faster your flight, flatter trajectory as well. It may require a little more tuning, more attention to your release and consistant anchor, but the increase is noticable.
To really notice the difference with a chrono, you need to have it set far enough away for the feathers to "stand-up" after the initial realease.
Also, straight fletched have a bit more speed as well, but the arrows aren't as stabilized in flight as the helical fletched ones. So form, release and follow through must be flawless if you want to group well using straight fletched arrows.