The seat belt hard points are fairly time consuming. First, each seat gets for seat belt hard points, the inboard side gets one for the belt receptacle, and on the outboard side there’s one for the inertial reel, one for the the shoulder belt, and one for the lap belt. We’ve elected to install the same 3 point inertial belts in all four positions. The factory installed the front shoulder hard points for us in the carbon beams, and the rear shoulder hard points are just through bolts installed in the spar’s angled bulkhead. The other three per seat are AL blocks (about 1″x2″) that are drilled and tapped for 7/16″ bolts and floxed and BID (3 layers) onto either the keel or the fuselage side. Once the layup cures, the hole has to be re-drilled and re-tapped. Say goodbye to a whole weekend….