I use a cheap ebay 4x32 shotgun/pistol scope. No riser. The elevation is adjusted to the max range. It has multiple aim points for different ranges. I found that the longest range is about 65 yards and anything under 25 yards is dead on the center of the scope.
It is mounted low to the marker and I use a killjoy roc stock so I can aim with a full mask on.
Oh and tymcneer please buy perfect circle and drive these costs down...we need sub .15 cent per round prices.