My solution is to put a tiny dab of silicone seal in the
offending corner areas. Once it hardens, the covers
never again catch my moustache.
Similar to Ron's suggestion, a quick, thin bead of hot glue can cover
lots of bases, including air-tightness along the coverplate edge at the
mouth area. Trim when cooled with a blade, if necessary, and easily
removed and replaced as needed. However, let me say...
Now, really... what are you guys all complaining so much about???