First, it sounds like you have
way too much compression. The Hi-Grip wheels don't compress much, so you've got 1/2" of bow to the Frisbee, assuming your outer wall doesn't flex. We found that reducing the compression until the frisbee rode flat on our deck improved our shooting tremendously. Of course, taking the tools away from the guys who were continually trying random adjustments to the shooter wall helped tremendously, too ...
Is it hooking towards the wheel side or towards the wall side? Does your outer wall have some flex at the end or is there a bracket right there? Is the outer wall straight off the wheel? Does the outer wall extend past the tangent point of the wheel?