Composite fan blade platform includes forward and aft portions and transition portion therebetween. Platform mounting holes extend through increased section thickness in transition portion and conical countersinks centered about centerlines of mounting holes extend into transition portion. Bolts include bolt shanks extending away from boltheads through center bolt holes in conical load spreaders in conical countersink. Boltheads engage conical load spreader. Bolthead is disposed entirely within cylindrical counterbore into top of load spreader and engages shoulder at bottom of cylindrical counterbore. Radial gap between bolthead and cylindrical counterbore surface of cylindrical counterbore may be filled by filler or filler ring. Bolts may join platform supports to disk hooks attached, fixed or joined to, or integral with disk posts of disk. Nuts threaded on threaded inner end of bolt shank may secure bases attached to platform supports to fan blade platform.