Omega,
There was a company in Norcross ( 4th world) called" First Strike"
that makes a 1st class conversion for rear apertures. The replacement aperture can be had with a full or half length hood , with changable inserts and a variety of aperture diameters. They also can install a super rear base that rides on 3 stainless steel rods and can be had with .25 or .50 minute wideage adjustments. I had one of these installed on an AR-10, liked it so much I ordered the kit for an AR-15. The half length hood was a super idea, as it gives glare protection but still allows you to acquire the sight picture quickly. Can't come up with the Phone no. right now, but if you can't find it, PM me and I'll look it up.