Hi Kevin,
We took our new Lunar Delta TI twin axle out for the first time this weekend. Ours has been upgraded by Lunar to max load of 1700 kgs. We have four motor movers fitted so needed the weight upgrade. We tow with a Hyundai Santa Fe 5 seater 2.2 CRTD. As mentioned by others you need to drop a gear for long hills, allthough it hold 60 mph on the motorway with ease. Prior to this we towed a single axle Hymer Nova 465 with a max weight of 1600 kgs. It returned a credible 30 mpg towing and local trips back and forth work.It gives 37 mpg at 70 mpg crusing speed on motorways.The only down side is the low nose weight of 88 kgs for my model. We have to travel with only one gas bottle in the front locker and the water heater has to be drained (it is forward of the axle line)The rear of the Hyundai sinks a bit lower the with the Hymer and the van rides slightly nose down. I will look to measure and fit Grayston rubber inserts to the rear coil springs as my model does not have self levelling suspension.
Mike.