For those of you that have never seen it before elsewhere, this is how to cut a circle in a dome the cheap way.
After checking all your trace out lines a few times take a drill with a sharp bit and drill along the inside of your traced area.
Next carefully wiggle your drill side to side till it connects a few adjacent holes together in a few areas. Then take a hacksaw blade and cut alone the dotted lines.
Take the curved side of a large rasp and file till you are a hair past you layout lines.
Flip the dome over and use a finishing rasp to take off all the burrs.
As you can see the holoprojector ring fits perfectly.