I just did the same mod yesterday... removed the cannister, drilled out the fuel filler neck, and installed the S4 system. I wasn't completely empty, but was able to put 5.5 Gal. into the bike - right up to the top. When you fill your bike that full, you need to ride it right away or risk having the excess fuel potentially flow out - IF you're parked on an angle. After filling, I rode 30 miles then parked. The fuel level was then back to where I normally used to stop filling the tank - nice.
I'll experiment with the syphon properties of this thing in another 200 miles or so...
I don't have the S4 system, how much more range could that give me, if I'm already using 6.1 gal.?