I have built a number of chicken wire covered (removable) light weight fencing panels from my allotment from tantalised 19x38 timber. These are screwed together with 6mm exterior ply triangular bracing pieces at the corners (on the back). Unfortunately the ply (treated with marine varnish) is starting to delaminate at the edges. Any suggestions (a) to improve the life if the ply, (b) an alternative to the ply used?