No. Do not use 23 gauge slight headed pins. Your Grex pinners are designed to only drive headless pins. When we developed our first pinner over 10 years ago, our testing showed that a tool that drives both headless and slight headed pins had a significantly higher risk of jamming which eventually resulted in tool damage. The reason is the looser tolerances required to accomodate both types of fasteners. So we decided to use purely headless pins. Holding power of a fastener comes from friction along the fastener shank and a combination of toeing and/or angling shots; not the head. And if you want to use a 23 gauge fastener because of the small hole it leaves, then why put a head on it to make it bigger?