Dean - ISP 2 piece lateral head support system used on my red. Requires fitting/forming aluminum blanks to your cage tubing. Both their 2 piece lateral and 3 piece head surround system are sfi 45.2. On their website, I see they offer a third bolt-on option: ready to install which does not require custom fitting/forming aluminum blanks to your cage. This third option did not state sfi 45.2 in their ad.
With their custom fitted head support, you measure and provide your desired dimension for helmet clearance. ISP fabricates with sfi 45.2 foam to match exactly your requested helmet clearance dimensions. Think on this; you need clearance to move your helmet to see the tree, but not so much that you can easily look back over your shoulder. My helmet clearance is 1/2 inch on both sides, with the foam pad angling out for more clearance moving to the front hoop. Alan