As I got my truck in September I mounted a set of mud flaps under the deck like most trucks have and had nothing but problems with them.
I contraptioneered some braces as to prevent the flaps from hitting the exhaust pipe and from the flaps flying up not doing there job, but those braces got bend out of place a few times over the winter until they broke.
Instead of contraptioneering another set of braces I got me a set of tractor quarter fender from Minimizer and mounted them under the deck in place of the mud flaps.

 

That is a great idea. I wonder if i can modify them to fit behind the tires and be inside the skirting.

 

The fender slide onto a 1 7/8 or 1 15/16 tube mounted to the frame the fender is 1/4 inch poly and I think it would be easy to trim if need be.
A strip of poly that suppose to be mounted atop with Minimizers advertising on them I mounted to the bottom to extend the fender a bit.

 

That should be easy to trim. With my flaps back so far I always throw/pack mud on the underside of my flatbed. Those should stop that. To help with cracking from rocks in sub zero temps I think lining the inside with metal and using rivets to attach.

 

I built mine into the bed:

 

That's a nice bed. I didn't build mine, It came this way. I don't need anymore weight ~9,300 lbs as it sits above.

 

I'm right at 11k on my truck. The liners save me from having to pack an additional 7-800 lbs of mud around..

 

I put something like these on all our flatbeds, problem solved.


http://www.nationalfleetproducts.com/Flattop.html