5th Gear Towing again

I know we have all been down this 5th gear towing debate before, what I will say is that I have just come across the Nullabor with the 20ft van on and was in 5th probably 96% of the drive to Pt Augusta, What I will add is this, I noticed that my right foot was only about 1/2 " down on the pedal, the vehile seemed to be rolling along without any hard work until I got a head breeze East of Ceduna, it was then on some sections and uphill runs I dropped it down to 4th, What I did notice was that it seemed to roll along easier with the Van on in 5th at 75/80kph than it does in 5th with the Oversize sign up and trying to maintain 90/95kph, It is amazing just how much the sign can knock the performance,and of course the vehicle had done 575,000 + before the gearbox was overhauled and 676,000 before the Transfer Case was rebuilt so basicly I cannot see what all the fuss is about concerning 5th gear towing, I think it is harder on the drive train with the sign up than what it is towing, and I know if any other truckies read this they will agree, when you have more weight on a combination the better it rolls, and of course a gearbox is there for a reason, as soon as you feel the engine begin to work you drop down a gear , what I mean is you don't try to drive up a just to see how far it will get in a gear but I guess there will be some who would try to drive Cunninghams Gap in 4th,
This is just My opinion, remember that, any know-alls can do what they like.