Marking Skin for Rivets - Measure Twice, Drill Once (or maybe measure more?)

Marking the rivet holes for the inboard leading edge rib.  Measuring per plans for 1.5" spacing I can only get eight (08) holes on a rib.  Hmmmm.  All the pictures I have seen and the plans show nine holes...

Here is my initial marking for the rivet positions at 1.5" spacing

Setting the 1.5" spacing with the rivet placement tool

That's marked on the center of the rib flange from just within the trailing edge to the leading edge end of the rib.  With the 1.5" spacing I can only get eight holes.  Is that enough?  On the plans the rivet locations indicate nine locations:

Plan clearly shows nine rivets on the top flange and eight on the bottom

I checked the plan and the first rivet location (at the spar) is just inside the trailing edge of the rib.  The second rivet location measures about 3/4" from the first.  Then they are evenly spaced at 1.5".  Even allowing for the 3/4" space between the first two holes I can only get eight.  I think the best thing I can do to meet the nine rivet requirement is to adjust the space between the rivets.  Maybe making the space 1.25" instead of 1.5" will work?  I'll try that and get back to you...

Thanks for checking in -

Greg.