Thanks to all of you. Here are the answers to your questions:
Paul, I did recheck all heights and other dimensions at least three times.

Robert, the gap is the same on both sides

Rob, for the three forms in the photo the spacing is 6" form face to form face

Reg, they're close to the center, but not dead center. Form 9 is at the center of the strongback. I did check spacing of the bases. They are where they should be.

Robert, a straightedge across 10 and 11 hits 10.5 and does not touch 11. That agrees with the plan, as 10 and 10.5 have rocker value of zero, while 11 has a rocker value of 1/16".

Kevin, that was an interesting exercise. As I went up the forms the gap disappeared at about 1/4" above the waterline mark on the form. On the more horizontal portion approaching the keel the gap shifted to form 11. See my second answer to Robert for the reason for that. Yes, the gap is the same both starboard and port. The forms do have a waterline mark, but Jay Babina told me in an earlier thread not to use them to settle any form placement questions.

Bill, the forms were all placed 12" from form face to form face, except form 10.5, which is 6" from surrounding forms, also form face to form face.

Thanks to all of you for your help. It helped me to review all of the points you raised. I'm inclined to ignore form 10.5 until the strips do start to touch it, as they apparently will just above the waterline mark. Since that is the only form that is not 12" from the next form I can't see that not stapling to it for the first couple of inches only will hurt the kayak.

Howie