Further info:
My understanding is that Hyundai quote weights without driver, so to compare with other manufacturers who include the driver I think you add 70kg - and use this figure for %ages.
The 1.7 SE Nav weighs 1425+driver with towing limit 1400 which must be to do with the test restart gradients with the manual clutch as the same model with DCT weighs 1470+ but max tow 1600.
Of interest there are far less 2.0D models on forecourts but the same variant manual gearbox weighs 1587+ and the 182bhp has a 2200 limit.
The 1.7 stipulates a 100kg towball limit, and the 85% is around 1275.
However as stated by others the maxim should be lighter van heavier car, with an 85% ratio being a good guide. .
Additional info:
solo driving with my SE Nav 1.7 (lately with lockdown on infrequent shorter trips) I am averaging nearly 49mpg (calculated from what I put in the tank not from the dashboard!) - best tankful over 53mpg mostly a couple of longer trips prior to lockdown.
I have a fixed swan neck fitted which is fine with the reverse sensors and helpfully is clearly visible on screen with the reverse camera. If you google bars for the car there is no bumper cut or removal to fit the bar, and dedicated electrics do not require remapping.
Hopefully I shall get some good towing miles under it's belt later in the year!
All the best!