Yeah, Doog, the hissing you're getting is normal, I built one of those exactly the same and had the smae problem, and at high gain I also have the same with the volume on my guitar? I guess it could be cheap pots and wires, but I dunno. Is it extreem hiss or just very mild and only noticable to the pedantic person holing the guitar (because it's true, I don't know why, but as soon as that guitar is in your hands, suddenly the fine details become noticable when you couldn't hear them when someone else was playing).
I think it's a result of the extra resistance in the circuit.