I think it would be worth running a test with the bug screen removed just to see what happens. If it doesn't help reduce the temp then you know the bug screen doesn't hurt airflow but if it does then at least you know and can take whatever action you decide.
Our 33 with a 99a 265 ci engine 3.78 rear end tows the caravan that weighs about 900kg at 50-55 mph all day in 35 -40C days , stock cooling with stock fan on the generator ,never over heats, most times around 75-85 C.
Lawrie
