rambling,
sorry if I came across as brash and "unmeaningful"... It is just that I have actually towed a 4.5T plus boat trailer with a 300tdi.
It wont matter if you throw another axle in - it will still be pretty ugly method of travel for highway distances. A 4.5T triple pulls you backward not twice as much as 2.5T double (the other boat I tow with no issues) but it seems more like the thing is 6 times as heavy! It really is that slow. The 15 or so degree incline going up Green St in town is 3rd gear low range full noise 50km/h. Obviosuly no momentum but even still on the highway with a 300tdi I wouldnt be surprised if you end up playing with the little lever.
Best of luck to your buddy - make sure the cooling system is A1 and that he plonks in a new gear bag and HD clutch while doing the chassis stretch.
Photos would still be awesome!
S

