I've gotta say...the puckered spots on the top skin at the F-708 bulkhead had been bugging me all week. I decided to drill out the rivets and make up some shims. The drilling went well and I soon had 22 holes to fill back up.

After checking the gaps, I decided to use .032 shims at the top, .025 around the curve, and .016 on the sides.

Here are all the shims. These are all 5/8 x 5/8 and of the thicknesses mentioned above.