Don't think too harsh of him for bypassing. When I had my H3 I did that same rock, just took an easier line. He's not too experienced, and like you said, he's off road and thats the key thing. 
I didn't notice any issues at all having the window open. I never heard it clank about or anything like that, but if I were in tighter, more wooded trails I think I'd keep it closed, just to be safe.
I didn't notice any issues at all having the window open. I never heard it clank about or anything like that, but if I were in tighter, more wooded trails I think I'd keep it closed, just to be safe.