If the screws strip the thread in the clutch, you have three ways you can go: buy another clutch-half (if available), tap out the stripped thread and fit a larger set screw, or fit helicoils to the stripped threads. I like option 3 best, because the helicoiled threads are very unlikely ever to strip again. As I think you now know, it is not necessary to tighten set screws all that much; they bite into the soft crankshaft, and the soft key, fairly easily.
