Yamaha YDX-Moro Rear Shock Upgrade

The Yamaha YDX-Moro isn't well suited for a coil rear shock. As seen below, the leverage ratio isn't very progressive, and becomes regressive in the last 17% of travel. 

Regardless, the tolerances around the Yamaha YDX-Moro rear shock are very tight. Although a RockShox coil shock will successfully bolt up, at full compression the coil will hit the frame. A Fox coil shock or Bomber CR coil shock uses a coil with an outside diameter 4mm smaller than the RockShox, which might technically work but with coil bulging it might still hit.