I take my vented lowers off in the summer on my Road King. I keep soft lowers in the bag if it rains. I know a lot of folks say there isn't a difference (i.e. heat on the engine) between lowers on vs. lowers off and frankly I don't have a quantitative answer. I do know this; below about 50mph it gets hot on my legs with lowers on, even with the vents open.

 

I had lower doors closed and it was hot here (Finally). And decided to open them and Wow did I feel more heat from engine...Figured the extra air to motor was a good thing...not that uncomfortable for me...I'm sure Harley CO has done extensive research on vented lowers and effect on their engine ????
Hap

 

Remove the bolt pivot hardware top and bottom drop it down at an angle,cut a 1/2 inch slot out of the thin top piece above the long slot 1 inch from the inside with sharp side cutters.Then you can remove or install with ease and they will close or open with no problems.