I ran a metallic clutch in my sled puller. Metallic clutches are that way. I told everybody it was like having a toggle switch on the dash. The clutch was either in or out. No middle ground.
Now try imagining trying to take off with 30,000# of dead weight behind you. Lol.
One thing about it, in 15 years of sled pulling my 454 NEVER managed to make that clutch slip.....and that was with a stock 12" Borg & Beck pressure plate. When I tore my truck down to put a sintered iron disc in it my son put that old metallic clutch in his mud truck and beat on it some more.