I also wound up with a cowl-spinner gap similar to what you're seeing. After 60 hours now on my 8A there is no evidence that the spinner plate has ever touched the cowl. The engine has sagged a bit but the gap remains about 1/8" all around.
When you run the engine with the cowl off, watch the engine closely on start and shutdown. Most of the "shaking" is rotational with very little up/down or left right movement.
Hope this helps