The instructions for mounting the seat pan say to redrill the tabs using a #40 drill. That works for the pop rivets; what about the center hole? I’m thinking #21 drill-right?

The tabs that seem to be for the shoulder straps are solid; no bolt holes. The airframe serial number is embossed on the starboard tab. The instructions show the correct tabs as being predrilled. Am I missing something, or I just need to drill them? 0.25”?

Thanks - Michael