This si one of the coolest fuzzes I have built in a long time.
There are quite a few mods that I would recomend.
Instead of removing the posision 2 tone option that sounds thin, I simply doubled the cap value, and it became very usable.
I also adjusted the dark setting (nr.3) by lowering both the 6.8nf caps to 4.7nf, and it turned out much better.
I also used a 6-way switch and added the 3 extra tone options found here: http://www.guitarscanada.com/showthread.php?53902-Roland-Double-Beat
All of them sounds better then the stock options. Higly recomended.
In addition to these mods I also added a 500k log pot to the input as a pre-gain, that gave me a much wider range of tones.
And finally I replaced R7 with 250k linear pot, with a 33k resistor going from the voltage track to lug 1 of the pot, then wiring lug 2 from the pot to the transistor's collector, and then I had a pinch/gate control. Be aware that you will loose much of the sustain when the gating kicks in, but it sounds quite cool and removes all of the noise issue. Specially the spot where the gate starts to kick in is very nice. This way you get something that sounds a bit like the pinch/gate funtion on the ZVex pedals.