I have one guitar that belts out a huge signal from the neck pickup. I was able to make the first stage just start to distort. To correct this, I have changed R5 to 1K and R3 to 4.7k also I have un- bootstrapped R4 and directly connected to ground. I thought the bootstrapping was a good idea – I must have eaten too many Twinkies that day. C30 and R29 are still optional but could be used to give treble boost or hi/lo gain boost etc.
If you have already obtained the earlier board rev, you need to cut the trace from the emitter of Q1 going to R4 and ground that side of R4 to the ground plane.
I am posted a link to the new board rev here and obsoleting the schematic and layout in the old post. All I did was eliminate this trace and add a couple of wire connection pads to allow making R29 a POT for variable gain. If you have the old board it will work just fine – with the mod described above.
Couple other minor notes: C16 may need to be increased to 22pF or so if you have a sluggish crystal – had one out of five that needed the bigger cap. Also with the mods above you may find that C21 should be increased to .22uF or more depending on the range and level of treble boost desired.