Seeing as various people have helped by posting details of their projects I thought I'd share some pictures and problems I've had.
First up, there doesn't appear to be a voltage crash bend, I followed the power input on the circuit but there doesn't seem to be a point where you can solder a pot across. If anyone can prove me wrong that'd be great. The tomne switch, high cut swith and the deep crash button mods are the same, but the deep crash button seems to be very hit and miss.
This picture shows the circuit board with teh smaller of the two chips, the wires from the two resistors are both connected to the 4th pin in from teh bottom right on teh chip, they go to a pair of 4k7 pots (lower value'd be better, but that's all i had) and create a high cut with ring mod/distortion and a distortion. the wire going to teh tone swithch can just be seen bottom left.
This picture shows the body contact points controlling pitch and the unconnected pots and bolts. Using these four controls makes the thing scream.
Detail of the deep crash and tone switch, like I said earlier, teh deep crash is a bit hit and miss, going to fish around a bit more tonight to see if i can find an alterantive.