Dunno the 'proper' way to do it but if need be I'd probably use a disk of paper or cardstock to shim it and use clear nail polish to glue the disk in place once I found the right thickness. That being said, I thought those screw-in stems were adjustable. I thought it was possible to rotate the stinger a bit to compensate for thread wear. Maybe have to warm the stem up a bit to get it to turn... not sure though because I never tried it. I don't have any pipes like that.