What touch and go said is about the best way. Also, when using very slow cure glues, like tightbond, I always moisten the outside of the sheeting with water in a spray bottle, so that it becomes more pliant. This allows the sheeting to flex with less springyness. I also cut the sheeting overly large so I can put pins in at angles on both sides of the ribs. If you are about 3/4 to 1 inch longer than needed on both sides of the plank, you can cut and sand the planking so that you leave small curves where the center planking joins the leading and trailing edge planking.

I have gone to planking with thick or medium CA, that has been stored in the fridge, so it has a longer cure time. It allows the building process to go so much faster and lighter than tight bond or many of the other resin glues. You may want to consider using medium CA for your bulsa joiners, under your cut out area. If the area is large enough to get your finger under each joiner piece you can make the repair very quickly. Just don't glue your finger to the joiner, like I have done a few times, because I used too much glue.

Good luck with this somewhat frustrating repair!!

Mike Boyd