Just a thought... I purchased a sheet of .063ga aluminum to replace the missing rock guard on my Sovereign
. After I get it trimmed to size and radius bend the edges, I plan on laying out the letters AIRSTREAM across it and drilling very small holes around each letter and backlight it with amber LEDs. I will polish it and clear coat.
Just a little razzle dazzle during night trips too.
I thought about going with the original plastic, but have yet to see a guard that holds up over time. Aluminum is what AS should have used from the start, IMHO.
If you aren't worried about aesthetics you could epoxy a similar shade plastic to the inside of the guard. Also, with radial cracks that tend to grow, you can arrest them by drilling a hole at the end with a small drill bit. A hot paperclip works too.
Hope it works out like you want it to.