I just did as you described... I am tiring of the new trailer smell so I installed a max air 2 over my fantastic fan vent. The max air 2 is supposed to have 50% more vent opening... You can buy a cover that is the same size as the fan (about $110 canadian vs. $39 for the max air 2)
I only run it on 2 so it should be fine. It is thermally fused so that if it get too hot (restrictive flow) it will not burn out. I have been running it all last week and it seems to be flne. I have also opened a window to let the air move into the trailer more freely. Of course it is a window that won't let the rain in also! (kitchen on my unit) I also propped the bathroom door open.