The shape of the limb pad is also different.
The Gamemaster limb pad has the same contour as the limb and is designed to for the limb to be bolted down flat. The pad on the ILF riser is flat and desgned to only make contact with the limb "rocker." Because of this, the limb contact is virtually the same across all preload and weight adjustments.
If you want to experiment, I would go with the ILF riser. The only difference between the Gamemaster and any other bolt down takedown is that the riser is metal and shaped funny. Aside from that, there are no adjustments.