I generally refrain from using plastic (nylon actually) clevises on anything larger than .40 sized.

But here's the thing of it, I've never had a nylon clevis fail on a model in flight, only when making control adjustments. I have had a metal one fail because the threads stripped out. (Combination of grime in the threads and vibration ground away the threads on both the clevis and the link and resulted in a elevator linkage coming loose in flight. fortunately the elevator jammed in neutral. The landing was a bit harried)

If you do use nylon clevises, invest in a 2-56 tap so you can cut threads part way into the nylon. I have broken nylon clevises by forcing them on to threaded rods with out tapping them first. I think the stress and strain of twisting then onto the links without tapping first shortens their life.

Great Planes sells a nice set of taps with matching drill bits, sized for typical modeling use for a pretty reasonable price. They are repackaged industrial quality taps, and of surprisingly better quality than the hardware store brands.