I find that advice somewhat incorrect. I have a cowl (giant UcanDo) that is sized for a 2 3/4 inch spinner but the engine, SPE 40, installed takes a 20X8 prop. I can't fit my 20X8 wood props inside anything smaller than a 3 1/4" aluminum spinner and will probably have to use a composite APC or go with a visually over sized spinner or none at all.