Window Frames

A few of the windows on our new Big Country have a gap between the metal frame and the outside wall. Usually the gap space changes around the frame from no gap to maybe 1/8 or so in one of the corners. Kind of looks like they are not square against the wall. My question...can I fill this gap with silicone? Nothing is leaking but I seem to remember something about "an ounce of prevention"

Thanks much!

SJH..The same thing happenied to our 3300SK Sundance. Your commit about an once of prevention was what made me squirt a little Pro Flex RV sealant into the misaligned joints. My windows didn't leak either but I felt better about it.