I recently had a look to see if I could find a trace of this pedal but there is nothing to be found. I think there would be a fair bit of interest in this as a PCB.
I have an SL Drive and I built a Captain Crunch (which is very similar to the Angry Charles: I guess the Crunchbox is what the Angry Charlie was based on).
They are close but still sound different to me. The SL has a bit more bite in the gain, and more distortion at the lowest gain setting. The Captain Crunch is smoother, and it cleans up at lower gains.