Hi Charles,
Thanks for your question. The longest staple we have is 9/16″. That would give you about 3/16″ penetration into your form, which is probably not enough. I would recommend using our B/18-080 3/4″ length brad nails for this. This would provide 3/8″ penetration into the form, which would give good holding strength, while the glue sets. Also, if your plywood will have some pretty good bend to it, the brads would be the recommended solution.
I hope this helps, but if you have any other questions, please let us know.
Thanks!
.
