I have both my sporsters "floated" like ice described, and both use the factory screw. At the very front of the forend where the forend once came up and touched the barrel I now have an 1/8" gap.
Accuracy from both rifles both improved a little when the rifle was sandbagged on the hinge pin, but not much. The big improvement came when shooting off a harris (type 1a2-br) bipod. With the forend touching the barrel any torque from my shooting form twisting against the bipod was transfered to the barrel changing the harmonics. With the forend floated and the forearms ability now to twist a little freely and absorb my shooting form imperfections, my groups from a bipod dropped around .25".
I have to assume that floating the barrel would have an effect in off hand shooting as floating the barrel would transfer less twisting caused by the way you hold the rifle making the harmonics more consistant.
I made my "oring" out of a 3/16"ID rubber vacume cap. I cut it down to the thickness I wanted and installed it and haven't messed with it since. The rubber holds the screw in the forend when I remove the forend to disassemble the rifle for cleaning (like after a rain) and the rubber absorbs some of the twisting, torqing, and vibrations from the forend.
I also tried putting a peice of rubber between the front end of the forend and barrel to create a pressure point. My 22 mag didn't like that one bit when shooting off a bipod, group sized sored. Removed the pressure point, returned to "floated", and it groups very tight again.