Don, maybe the full scale uses metal plates to reinforce the spar. Many WWI planes have through the spar holes with plates and bolts.. At least that's what I have seen in my searches. And yes of course the hole is the weakest spot but that doesn't mean that it will necessarily fail. That would depend on the loads on the spar...
Donny, yep I have slowed down a bit. and I need the excersise I get from golf!!!! but I have been making some detail bits so all is not wasted time lol.