My thoughts were to put 2 foam panels (cut same size as grill) but under them, so when I screw the grill back down, it hold the foam in place. Yes you wouldn't see the cone through the grill like now, but who looks at it... (well some of us do LoL). With 2 cabs (which I use rarely these days), correctly placed, I don't have an issue, but I do get beaming (that I care about) with the one stereo box. If you have decent monitors and side fill (and time to dial it in), the issue IMO goes away. E.g. stereo wedges in front (dedicated), a bit extra through the side fill (with some bass and drums), boxes well placed behind you, time to tune it with the fold back engineer, you can make a very nice "guitar" zone that's got some space to move. But not all systems provide for this, and when you are an act on a multi line up concert, you don't generally get this latitude (unless you are headlining).