The red poppet will be the highest flowing poppet available for the F2. After testing different poppet valves we confirmed that the standard red poppet in the F2 flows more than the air input fitting feeding the system. So, a poppet with higher flow than the red makes no difference in velocity since the restrictive point is the fitting and not the poppet.The Fusion Engine is able to flow more through its poppet valve than the F2 since the Fusion Engine has an accumulation chamber behind the poppet valve on in additional to being fed from the input line. The F2 is only fed from the input line so it is not able to dump a large volume of air as soon as the valve opens. While this prevents the F2 from reaching the upper most velocity range of the Fusion Engine, it does make it possible for the F2 to be noticeably more air efficient at normal field velocity limits.