Actually you can space out a spinner and have done it many times for just the reason you speak. One of my favorites is as old as model aviation itself and it goes like this: Use an old APC plastic prop (no wood props) cut the blades off and sand to a round blank. Now just use a bench grinder or face sander and thin down to the exact thickness you need and what you have avalible crankshaft threads for. I currently have two ships now in my fleet that are done this way One of them is a TT.61 pro. I am sorry but am completely befuddled and cannot post pictures with the new forum but would have otherwise. Also still unable to separate the reply into paragraphs but there is one other way to do what you want to do. That is simply use a propshaft extension from 'Fox Manufacturing' which are made in quarter inch increments up to three quarter inch. The three quarter inch extension is currently in use on one of my airplanes, John