Read the kit instructions... the test pilots for Sig tried assorted engines... the little thing was designed for maneuverability, not speed. Its structure is designed around a .09 to .15.

Yes, you can improve speed with the bigger engine. but maneuverability suffers too much. (same roll rate at same airspeed but loops get big fast as weight goes up) Stall characteristics can get downright violent if its too heavy. Bad stall characteristics = broken airplane when trying to land it.

You can improve speed on anything with a bigger engine... but is it really an improvement when it rips the wings off?