The PUG is a no brainer, even if you are camping on weekends only. A solar blanket from Cabellas does the job equally well for a lot less money.
Regarding leaving the bunkends open or closed, I'd closed them as a rule and if it's raining one weekend at the time you want to leave, then leave them open for that week. The location is a factor, if you feel the trailer is safe where it is, there is not much to worry about, but you know it's easier to enter through a canvas. Kids with nothing to do might want to get in and look through your stuff. Not a pleasant thought.