Yes they are all modern wagons with pin-point axles. 51 Dublo wagons would be a struggle even for a Dublo 8F, especially as this is the version with the ½" motor. The ringfield motor gives it a bit more T.E. (presumably due to the extra weight, as the locomotive slips well before stalling*?). Somewhere in the 'bible' there is a list of the expected loads up a 1 in 24 gradient (The Acho elevated sections). I think it is a bit optimistic however.
* or at least mine does!
This was one of the surprises discovered while messing about trying to find the best hauler, the 1/2 inch 8F can actually pull more than the ring field motor version, I suspect the ring field upsets the balance of the 8F so less weight on the front wheels causing slip.
As mentioned before my 1/2 inch 8F is a converted 2rail, one side steel wheels the other seems to have nickel silver, these wheels have more grip.
As for rolling resistance all stock is measured on my adjustable rolling road, just an adjustable incline, can select some HD stock to pass 1:40, have noticed that some pin point axles struggle with that, dirt, wear, wagon sides Wapping, etc can all take there toll over the years.
Pin point axle trains seems to greatly increased the rolling resistance on the curves, these does not effect as much non pin point.
Another factor I have noticed is momentum, heavy train has momentum, loco stalls or struggles on some section of track, the train itself pushes the loco over the rough section, trick of cause is getting the train going in the first place, great fun trying to drive the train, slight slip and reduce the power then apply slowly.
I think it is still possible, one or two very powerful locos, TH 9F, HD Co-Co, etc selected good running stock, 4foot curves even with non pin point axles