S
saxondale
you SHOULD lift the carpet up 2-3 feet at the very most, cut the underlay away from the INSIDE of the carpet gripper (about 1cm wide) fix your cable down, relay carpet, use blunt bolster chiesel to secure carpet (bolster chiesel goes where saxondale said to put cable)
if you are good / quick the carpet will not shrink back
either way is a good valid technique used everyday by the pro`s but for a guy taking his own carpets up............