Change of plans. While hogging out the rest of this with the SkilSaw would be faster, but less accurate, I got to thinking that since my framing is dead level, I'd use the router to carve out the areas where the steel is and use the SkilSaw to rough out the rest as those areas would be above open areas in the framing so it wasn't critical that all that area be 'perfect. The 'channels' would all be at the same level so (in theory!) there should be little to no shimming required to level the slab when it's installed.