ORIGINAL: thundercloud
Weight is allways an issiue for anything that flies.
Assunimg you mean excess weight, it's only an issue when it's in the wrong place and unbalances the plane. Otherwise, not always. eg, slope soarers use lotsa ballast to increase airspeed to penetrate in strong winds without affecting sink rate enough to bother about, and they don't even have a jet engine for propulsion.
Gordon