I have this on both my seats and love it as well. I flipped a car (barrel rolled) last year and watching the in car video, my head barely moves. It allows just enough room to turn your head to look around, but not enough for your head to gain momentum in a side impact (or barrel roll).
When mounting, this is how I did it:
1. Installed seat for comfortable fit.
2. C-Clamp headrest onto seat and adjust for vertical placement while in seat. The headrest has a cut-out or skinnier part towards the front. I like to line up the cutout with my helmet visor. This cutout allows you to use whatever peripheral you have left with your helmet on. The thicker part to the rear covers alot of helmet area and makes for good pillow when I fall asleep on the grid.
3. Mark the seat back with sharpie where the headrest crosses.
4. Add spacing material (washers or whatever) between the seat back and headrest to adjust horizontally (front to back). This again will better line up the cutouts with your helmet visor.
5. Drill holes (I did four 5/16" holes on both sides of the channel) through headrest and use as template to drill through the seat back.
6. Put fastener heads on inside (head side) of the seat and run through the headrest. Place whatever spacers (washers) between the seat back and headrest to fill and gaps created for horizontal adjustment. Note: some seats may be "rounded" in that are that you may need to put more spacers on the outer bolts to fill gaps.
There is also a flat tab on the side of the headrest which I use to mount my raceiver. I purchased a raceiver box from speedway motors ($10) and rivetted the box's standoff to the flat tab. At the start off the night, I put a new battery in the raceiver, set it to the channel, close the box and zip tie it. Then when I get in the car, all I have to do is plug in my ear buds near my head and I don't need to clip it to me or somewhere in the car that the ear bud wire gets in the way.
The bolt on shoulder pieces are nice also. $70 for the pair instead of the more expensive single pieces from other companies. I installed those on both seats as well. Had to cut them for belt clearance, but they work well. I bent the left side to fit easier inside the frame and bent the right side so that when I move my arm/shoulder out against it, it puts my hand directly to the shifter. No more searching for it to change gears during restarts or while spinning.
Hope this helps.