Winch Bumper Rubbing Fenders on Bumps?

I bought another member's truck here and it came with a Shrockworks bumper. After taking it down a dirt road for a back way home yesterday I noticed a pretty good rattle from the front left fender on some bumps. Contacted the previous owner and he said it was the winch bumper hitting the fender as it weighed enough to cause some frame flex and contact the fenders. Is there anything that can be done about this at all....? The fender seems to be tight as does the bumper at the moment. There are marks on the fenders from the bumper it looks like, more on the driver's side than the passenger.

 

Drop the bumper down? Should have adjustable mounting I'd think, what is the make of the bumper?
You need about a 1/2" between bumper and fender

 

Shrockworks bumper/

 

make sure u got bout half an inch or more between the bumper and fender. if u dont, try readjusting the bumper. these frames flex really well

 

I'll give it a go. It's pissing rain outside so next chance I get I'll give it a shot.