Hi Bob ..noticed your SE5a build slow down again..get them golf clubs back in the boot A simple test of the strength of a drilled spar is take a bit of scrap spar wood ..drill a hole and put a bolt through it .. now test to destruction .. bet you a golf ball where it will break Yup ..hole in one

Don not sure of your setup for the cabane to spar but an easy way to secure the top wing centre section is a right angle piece of metal..epoxy and bind with strong thread to both cabane and spar .. normally the thread can be covered with wood .. sometimes the real deal has rope binding at the top of the cabane to prevent the wood splintering..dont know about the nieuport though. Alternatively ..as I did with the Jenny ..reinforce the spar with the aluminium strip that holds the wing spars in position then you can drill to your hearts content (within reason) as the aluminium takes the stress. (see pic)The wing spar will be similar but in reverse. The functional landing and flying wires will hold the dihedral on the bottom wing and top wings. It will surprise you how rigid even a flimsy wing becomes solid when properly rigged.

PS though not scale .. I always like to sheet the under side of the top centre section .. why ? ..Because I always carry my bipes by hooking my hand under the top section ..saves sticking my digits through the "canvas"