Well, what you want to put on that is my Auto Rangefinder. Gets the elevation right for any practical range out to say 40-50 yards depending on the quality of paint you get to use. The called me Head Hunter for a reason.
Basically a do it your self project. A peep sight on the back which you already have but my have to raise. and a modified post on the front.
The post is a 2/56 threaded rod about 2 1/2" tall. Tape a 2/56" hole in different size brass fishing beads. 4mm, 6mm, 8mm, 10mm.
The beads match the diameter of the human head at a given distance. Just screw the beads up and down until you paintballs drop onto a mask on a milk jug at that distance. Drop of super glue to fix them and you are ready to go.
It IS Super Critical to have a consistent muzzle velocity. You can actually chronograph your marker using it.
Have pictures and illustrations. Building an upgraded version this spring that will extend my practical range out to 60 yards or so. Have drawings for it.
For info, anyone can e mail me at firstname.lastname@example.org