The 140 Cherokee had a shorter fuselage and a different wing. It actually started life as the Thorpe Sky Scooter and was a two seater. Piper initially made the PA 160 a full four seater, the wing was diferent again, having no 'wash out'. When the PA 28-140 was concieved it was a 2+2 having a limit of only 200lbs on the rear seats, and a wing with 'wash out'. How many times have you seen 4 adults climb out of one? The aircraft was certified in two categories 'Normal' and 'Utility'. I've forgotton which one is which but I think that you could only spin it in the 'Utility' category with no load in the back.