If you're towing fit an EGT gauge
I tow a camper/trailer with Peril (a Tombie2 chipped 110). Peril's got a bit of extra weight over a standard X-treme - maybe another 250Kg and the camper/trailer when loaded is probably around 900 Kg.
The camper/trailer definitely slows Peril down. Nevertheless, If I want to I can hold 110kmh on an open road and maintain a good pace up hills BUT what I find is that my exhaust gas temperature rises quickly on long hills with any more than a moderate gradient.
If you haven't fitted an EGT gauge then my strong advice is to do so and watch it like a hawk. It's surprsing how quickly EGT can rise when you start to work the engine hard.
From extensive reading on this forum I've come to the conclusion that I should never exceed 680 degrees Fahrenheit, so once I hit 650 degrees I start to back off. What this means is slowing down; simply changing down a gear and maintaining my speed usually does not see the EGT fall.