I have a PSA PA10, 18", "classic" with an A2 FSB. The rail on the upper is further from the bore axis than the typical AR15 so any sight I put on the receiver rail is too high to work with the A2 sight. I'd prefer to keep the old school handguard. I've seen gas blocks that incorporate a short Pic rail but none that are coplanar with the receiver rail on my PA10. Is there such a thing?