I did the same using nylon/plastic washers and a screw from underneath, but the washers are quite hard and not a long term solution as I think they would damage the case over time.I ran into the same problem 2 years ago. I lost one and then another would pull out when I took the top case off. The rubber degrades and gets sticky with age. I resorted to some old rubber washers and grommets I had laying around. I didn’t want to use glue and surprisingly, an old clay bar has kept things from flying off for 2 seasons so far. Also allowed me to shim/shave them so the box was snug and flush. Here’s a pic of the cobble. The felt pad was the last resort but didn’t try it (water retention?)
The shipping was just as bad 2 years ago when I went looking (dollar was stronger and no tariffs yet), so I decided to use the rubber parts laying around and made it a tight fit. I noticed over time the original rubber stoppers wear out and the top box starts to rattle on them and of course wear them down even faster.
