I want to build a simple PVC system to which I can attach a few tail lights. The best place, I think, on my bike to mount it is on the back of my Topeak rack. There is a little plate with two screw holes that will be easy to attach to (see left side of picture below).

My question is, if I drill a hole straight threw a 1" PVC pipe and use that to screw onto my rack, how likely is it that the PVC will fail where the holes are?