I used a hardwood block there that fills in between the mount and the saddle so that the top of the wing is secure to the plan, and tap the wood for the bolt. I us nylon, but you can use whichever you like, but keep in mind a steel bolt weighs 3 times as much as the nylon one. When tapped, shoot thin ca down the threads and retap when cured. Run the tap through a few times until the bolts go in smoothly, but not loose.