You do not need to bond it together. 3mm coroplast will work great for a .40 class sport plane, in fact Spad #1 was built entirely out of 3mm coroplast. The neat thing about 3mm coroplast is that 1/8" dowel is a perfect fit inside the flutes for stiffening the tail feathers and control surfaces. It is awesome for building wings, as it's easier to fold and glue than 4mm, yet almost as strong...and much stronger than 2mm.