We have had our radiator grill off many times fixing the rear bedroom hydraulic hose issues. We also have the L brackets but they were attached with 1/4" standard carriage bolts instead of machine bolts that you can get a wrench on. I thought this was an exceptionally "cheap" solution for fastening an item as big as a radiator grill on a coach the price of an Alpine.
My solution is to change to quality machine bolts and fasten them snugly.
Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra