Here's what to do...Go to Wally World or some craft storeand get some round self stick cork pads, like you'd put on the bottom of a lamp or bookends or such. Sometimes you can find it in strips or a sheet that you can cut to any shape you need. Also pick up some of those sewing pins with plastic ball heads. And a can of good paste car wax.

Wax the back of the riser - the wax will make it easier to clean off the stickum from the cork. Stick one of those cork dots or stripson the riser in about the right spot, then another one or two over that in order to build up the thickness some. Then take one of those sewing pins stick it in the dot. Obviously, elevation is adjusted by trying differentspots upand down with the pinuntil you get it right. You adjust windage by pushing the pin in further or pulling it out.