I don't like tapping plastic, and I don't think it was designed to be tapped. Once opened up it's too easy to strip. I think driving the screw in drives the plastic around the thread and provides better friction because the plastic remains tight. With a tap, you actually cut the plastic and all the friction is generated by tightening the screw as hard as you dare. When the plastic gives, you've got to replace the part. I know that Tamiya's philips head screws are a pain to drive in, but I use an allen head socket screw to create the thread. That gives better purchase with a strong driver, and you don't have to push down like a possessed maniac to prevent the screwdriver jumping out. Don't use the philips heads in assembly much either. Prefer pan head or countersunk allen screws for ease of maintenance (same driver does both, saves dicking around with two drivers).