I doubt you would be able to overcome the squealing and noise...
- You will need to put 150-220pF caps from G-S on all of the FETs (this sounds better on the stock Dr Boogey anyway.... per RDV's excellent advice!)
FWIW, I would:
1) Drop in a duplicate of the 2nd stage
AND/OR the below-
2) Raise the value of the cap that bypasses the gain control to 5nF (from 1nF)
3) Increase the coupling caps (22nF) between stages by ~50% at each stage
- So stage 1 couples with .022uF
- Stage2 couples to stage3 with .033uF
- Stage3 couples to stage4 with .047uF
#2 and #3 will fatten the sound up with out making it muddy by boosting the upper-mids and you will not have an increase in squeal/noise, and that will saturate that 4th stage (the 4th/5th FETs) a bit more. There is plenty of high end, however increasing the upper mids is going to change the sound a bit, and that will be subjectively either good or bad
