Wait... just noticed that you went with a tone control instead of a full tone stack (treb, mid, bass)... was that just to make it simpler?
Yes. The TMB controll from the hiwatt schem can easily be put back in place, but for stompbox-use, I figured 6 controlls and a swich was a little too much. I'm allso a "less is more" kind of guy, and I figured that a bright switch, a tone-, middle, and bass-knob and a presence knob was to many ways for me to change the voicing. A TMB-tonestack
always give me a headache, as I feel I have to twist knobs for hours to find a sound I like. Thats why I like the simplicity of a simple knob.
It would also recuire a somewhat larger layout, but it can easily be done. If you have the oppertunity to wait a few days, I might be able to draw up a new schem and layout with the full tonestack. I think this circuit could benefitt from the full tonestack, as I've heard much of the "Hiwatt-magic" lies in this tonestack. Nyway, it makes a pretty good overdive with the tonestack that I've added, but I would really like to change the tone-circuit a little, as it doesen't have that much affect on the sound. Anyway, I like this enough to use it as my main overdrive, but I might be a little biased.

Thats why I would like to hear what others think.