My thinking is that since the holes were drilled for the extra bracing on the lateral side of the spar - similar to the shear web on a rib, it likely doesn't weaken the spar significantly. That being said, however, I would't feel comfortable if my name was on the Airworthiness Certificate as the "Manufacturer" and therefore legally responsible for the final design and assembly. Thinking down the future, my main concern would be for you to consider how comfortable you would be selling it as a flying airplane as it is currently assembled when and if that time comes.