If you look closely you can see where I re-modeled the plank of 10" sapele so that I could get the deck curve out of the smaller stock - otherwise I would have needed a 14" wide board. Even though you can see the different wood grain, the fact that both sides are symmetrical makes it quite attractive - at least to my eyes.
Once I had both side of the coamings laminated, I decided to glue both on at the same time so that I could adjust each coaming where they join at the front and ensure a symmetric fit.
I also re-purposed the clamping cauls which JohnB describes in his instructions for the fore deck. I clamped these sideways at the front of each coaming and then placed a further clamp on them to pull the coamings together at the joint. It seemed to work fine and allowed for finer adjustments during the final glue-up.
It's a lot of clamps but it worked out fine in the end.