The medium sized Hi Viz X-coil recoil pad lines up with the screw holes on the spec ops. Just take off the spec ops recoil pad and use those screws for the Hi Viz pad. Since I wasn't using any spacers or brackets, I also put some plastic weld epoxy on before I screwed on the X-coil just to fill the gap.
~100 rounds of 3"/2.75" slugs and no problems, plus it's night and day difference compared to the hard knox "pad".
I didn't check to see if the large size Hi Viz pads line up with the screw holes, so you can try that one too if you need a bigger pad.