Horrace, I guess you have been flying a lot longer than I have, but I've got to disagree with the sandpaper washer. If you tighten the prop tight, using a proper wrench vs the glow plug wrench, there is no need for the sandpaper. The aluminum back plates all have some nurling on them, fore and aft. You can get as better bite on them that the sandpaper. Plastic back plates are a whole nother problem. All I have seen are soft enough that they will deform badly with a tight composite prop. I won't use them anylonger. They are a lot like the wood props, you need to tighten them up every day.

While on the subject of spinners and props, I'm finding that the low pitch props that I like, 13x4 and the like, don't have enough thickness to get the prop nut tight without a spinner back plate. The threads bottom out before the prop gets captured. So, I have to use an aluminimum back plate. I am fond of the Great Planes aluminum back with nylon cones. They are inexpensive and work very well.

Don