Here it is. Not sure about the efficacy of the felt, it did seem to warm up the treble and cut some sharpness, But the cable change stock (SE) to Custom Cans (XLR) was more important - my amp runs much better in balanced than SE, so...
But the dynamat is clearly audible. See the bright silver spots. Also note that I covered no holes. The mid bass and upper bass become firmer, (remove non musical resonances (the can is quite rife with them) impact is increased, but you do lose a bit of db's (but its not music). This helps keep the upper bass from affecting the low mids. An EQ (or OTL amp) can easily add back the bass (OTL gives more low bass 30-60 Hz than most transistors - even my Ragnarok 1). But not doing - you lose a spate of subtle details that add to this can as a reference of near legend. After my busy season is over (Labor Day) I'll finish my BC Crack - bought for the 600 alone)