Depends on what leverage ratio the swingarm is and what coil springs are available for whatever shock you decide to use. When I had a coil shock (Fox Vanilla) on my Super V (about 3:1 ratio), I had the heaviest spring Fox made for that shock at #1050 and it was still only stiff enough to get about 35% to 40% sag at best. I replaced it with a Manitou Swinger 4-Way Air that rode far better and I could run it at 25% to 30% sag. My weight was around 270lbs to 275lbs during that time.
On my current bike, a Giant Reign, I only have to run about 190psi to 200psi in the Manitou Swinger 3 Way Air. Strange that people of similar size report having to run higher pressures in the Fox shocks that Giant used on the Reign after 2005.