I got to talking this over with Herb today and he was curious about the difference having flaps or gear down has on VMC so we flew some test flights in his Apache. We got an 8 knot decrease in VMC with flaps down, a pretty good bit. We found about a 4 knot decrease in VMC with the gear down only. This for an Apache but you can pretty well extend this situation to any propeller airplane in a similar configuration. Some exceptions might be if the gear is not located behind the operating engine, and in that case the difference would be negligible. I can't think of any twin trainer props like that but there are a few military props that house the wheels inside of fuselage blisters that might qualify. Also, any flap setup not located within the propeller slipstream would of course not offer as much additional drag and turbulence as one where the flaps are located behind the operating engine. I can't think of a single airplane that fits that description right off hand. Extra points if you can.