I did the same thing that Chris stated above on my former 07 Montana making the repair about 5 years ago and never had a problem once I took the flexing out of the plastic. I used 4 or 6 inch (have to measure) barn/gate style hinges that spread out the area metal to plastic thus strengthening a larger area of the plastic. When I attached the hinge to the plastic I used 1/2 or 3/4 by 3/8 inch bolts with the biggest fender washer against the plastic I could find. Then cut off the hinge where it attached to the metal on the slide out using one existing hole and only having to drill one hole for the other to attach to the the slide out frame using the same screw to attach it before.
Life is great when you can scratch that hitch itch....
HDT 1999 Volvo VNL610 12.7 Detroit 10 Spd Eaton Manual trans. 430 HP, 1500 pounds of torque,
"The Beast" (retired) 2003 Dodge 3500
2014 RW 38GK14, solar panels with MPPT controller, Progressive surge guard, 2 group 31 AGM batteries, Morryde SLR4000, Titan disc brakes,