I have a MAN TGE based camper van. It is the 3.180 auto and it has a maximum towable mass of 2825kg. I have not towed with it, but have no doubt it will easily cope with 1800kg.
I used to tow my Fiat coupe track car on a twin axle ifor williams trailer with my campervan on a Renault master chassis with a 2.5 litre engine. Coupe and trailer would have been around 1800 kilos. No problems ever and would cruise at 70 mph on motorways without a struggle.
Contact Moran Motorhomes, if anyone would have experience, it would be them. No connection other than being a fan of Scott Moran (multiple British Hillclimb Champion). Kim