From the left side you really need to be looking at the distance from the cockpit window to the main entrance door. The Gv's is further aft.
On the right side most 550's have a 7th main cabin window. The APU exhaust area is different, the shroud is centered. The outflow valve behind the FO's window is square on a 550 and round on a GV.
On the right side most 550's have a 7th main cabin window. The APU exhaust area is different, the shroud is centered. The outflow valve behind the FO's window is square on a 550 and round on a GV.