Well, I tried it out on a gig last night - I really liked the sound, and the bandmates did too!
I'm not playing any slap, for which this would work really well incidentally, but the attack of the notes when you dig in is nice if you want it, and rolling the passive tone off to about 2/3rds takes it back to "normal" when the click isn't required.
I love the Compact, but find (so far!) that this gives the extra dimension in tone I was looking for, and 1 seems plenty loud enough, I really cant see any need for 2 with 1 cab.
Here's some pics, In typical fashion, it's not finished cosmetically, I built it at lunchtime, gigged in the evening. I'll probably knock the rough edges off sometime.
It's got Velcro now to stick it to the Amp to stop it jumping around:
[attachment=87995:Tweeter_1.jpg]
[attachment=87996:Tweeter_2.jpg]