TBH, a little load should not cause it to run hot, If it's modified the tune might be off and it's a bit lean under light load or not enough timing. If it's stock standard something else is a little off.
Once you are running at a decent speed the thermofan won't come on as the airflow through radiator should be more than enough to cool it. A couple of things that can cause cars to run hot is if the plastic strip between the top of the radiator and the radiator support panel is missing and also the right angle plastic strip under the radiator, this alters the airflow under the radiator and helps to extract hot air.
Our L67 was running hot under load. The problem was it didn't have enough timing for the amount of boost it was running due to the fuel. Once our local servo stepped up with 98 (so the missus would use it) I added timing and hot it run no more.