Does Drill Motor Mount Weaken OCC Schwinn Chopper Frame?

I weld my OCC builds(custom mount). Others have drilled a larger hole and weld a piece of tubing in the hole. Then the motor mount bolt goes thru the sleeve and prevents the tube from de-forming when over tighting the mounting bolts. I personaly not heard of an OCC bottom tube failing, only deforming.
http://motorbicycling.com/f3/integrated-motor-mount-jack-shaft-12284.html

I'm not in favor of drilling through tubes, but with the chopper I built I opted to mount the mount by drilling. I have had no issues with the chopper but have on a mountain bike that I drilled out the water bottle mounting hole to accommodate the magneto wires. The chopper tube is larger and stout.