Many have asked where and how to do the O-ring floating of the forend. The O-ring is placed on the forend barrel stud before installing the forend on the barrel. A little experimenting with size can be advantageous, but generally a 9/16"OD x 3/8"ID x 3/32" or 1/8" thick O-ring from your local hardware store will work. Some have used different materials like grommets, too. Nothing is written in stone, shoot the rifle first before trying it, it may not need any modifications. Some shooters also have good luck by using business cards placed in the forend to create a pressure point, I've used refrigerator magnet material with good luck on a mannlicher forend and many other forends, a 1" square added near the tip of the forend in the barrel channel secured with a little RTV silicone to hold it in place in the forend works. Each rifle is an individual, so what works on one, may not on another. Experiment with screw torque also, some work best tight, some just snug, consistency is important, so what ever works needs to be repeated each time the screw is installed.
Depending on your forend and barrel contour, you may need to sand the forend to completely float, or leave space around the barrel so the only contact it's making with the forend it at the stud, use sandpaper wrapped around an appropriate size dowel to do the sanding.
Tim