The rubber bumpers between the upper section and the outriggers or frame from the factory did not hold up for very long. Because of the type of material used, the upper being a non reinforced rubber and the lower breaking down, becoming hard and cracking from the UV rays. Other people have tryed many different types of materials.
I found that a semi-truck mud flap that is 1/2" thick works very well because it's reinforced with cord and has enough rubber to act as a bumper.
I cut 2"x2" squares for the outriggers/frame and mounted them with two offsetted screws to prevent them from spinning like the old ones did. For the uppers, I cut 5/8" x 4 1/2" to replace the gray rubber also offset these screws so the screw heads touch the lower bumper screw heads.
With over a year and 4,000 miles on them, they held up very well with no problems.

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Les & Patricia
2006 22ft towlite (replaces 97 21TL)
2006 Toyota tacoma pre-runner 4.0 L V-6 quad cab
w/ 98 chevy Powervision towing mirrors
2017 Chevy Silverado 1500 5.3 v8 (replaces Toyota)
2 Hobie mirage pedal drive kayaks

You can also use "road alligators" (blown truck tires). They can be cut to size and the rubber is reinforced. Just be careful when you stop on the road to pick one up.

Bob

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2014 FR Heritage Glen 282RK
2013 F250 HD 6.7L Diesel
Formerly Owned: 1995 22D Fun Chaser & 2901L Classic

I used pex pipe for my frame bumpers.
Use 3/4" diameter x 4", and drill through the first side and screw through the second side to mount and have the screws not exposed. The PEX will return to original shape, round, when trlr is up and gives a cushioned ride for the top when in the down position. My hi-lo has 6 frame points for contact. 2 front,2 rear, and 1 each side.
Cheap and lasts forever. Mine has been repaired in this manor for 3 years so far and over 16k miles, many gravel and off road.

my $.02
steve

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2002 ford f350, 7.3 diesel
1985 hi-lo funchaser
kb0nai
kd7ctk

My 1977 19 footer needs this same repair!
Thanks.
Erik