Drag from the flaps perhaps? During short field takeoffs in the 181 I leave the flaps up till about 40kt, then click on two notches and start to bring the nose up and let it fly when it wants to, usually around 50-60kt depending on loading. Using this method I have had a pa28 airborne in just under 100m on grass, but it was empty, I don't remember the winds being significant either.
Good points you raise there PilotDAR, Ill keep that in mind in future.