Stu, with the Saw's table waxed, and using only One magnet, is the one that lays on the table to press the workpiece against the fence strong enough to keep it from sliding across the table when pressure is applied against it? Just curious.
I know the one mounted on the fence to hold the work down against the table should be fine, since that is the strongest magnetic attraction direction. Also, does your fence have any tendency to lift at the back when using that hold down? I know that some folks with Biese clones have showed an L shaped gizmo hooked to the fence that rides back under the rear Angle Rail to keep the fence from lifting at the rear when using hold downs or Some jigs that are attached to the fence.