Yay! Let me be the first to award you your official Pest Control Merit badge for completing the very first, and best step in controlling rodents, or any pest for that matter - exclusion!
I made similar disks out of some plastic and aluminum I had laying around the shop. Fasten them in place with a wingnut and bar aluminum. Finding and sealing entry points should be everyone's first step. I can be the hardest, but is the most effective step.
In other mouse posts I've told a story of sitting in my chair outside at a campground watching little Yellow Pine Chipmunks go through their RV inspection routine. They'd run from RV to RV stopping at each cord and hose to look up to see if they could get in. Some would even run up the cord to check. One ran right past my feet and did the same at my rig. People fail to realize these little guys are professionals who learn the tricks of the trade very quickly. They have all camping season to find the best entry points on just about every rig imaginable. If you camp in a campground you can bet there's highly trained rodents checking out your cords and hoses. Its their job. I'm surprised at the number of campers who leave a compartment door open because it's easier to run the hose through the open door. kinda' asking for trouble if you ask me.
Great job with your blockers and thanks to grovein for sharing the link for the critter guard. That looks like a good product that should be effective. I'm going to bookmark that link for future mouse posts.