Just remember that ready made (metal) sitting figures, usually crew or drivers for vehicles, often tend to have very stunted legs to make it possible to fit them into the vehicle.
I once converted a sitting crew figure (an officer in a kubelwagen) into a helicopter pilot. And because of the glass cockpit, I couldn't get away with the legs as they were. Not in the least because his feet did not reach the craft's pedals by a long shot.
So I ended up cutting off the feet and adding kneehigh jackboots from another miniature (standing) to give him a normal posture...