I did not like the MRA X-Creen mounted with the clamp-on mount, as it put the spoiler too high even at its lowest position. At its lowest position, the spoiler was 3" above the top of the stock windshield and I did not like that.

Since it came with the bolt-on mount, I'm going to install it. But I need to drill 4 1/4" holes. I got the drill bit for plastic (the bottom one) and it's so much easier to drill than the one for metal as the angle is sharper.