I sent you an email to forward to Charlee. Thanks!
I've been trying to find some Graupner 3 blades. Their web site either dosn't show the big 3 blades or I just haven't been able to find them. Their website is a bit difficult to navigate. All I can find is electric props. I know they make bigger props, I have some of them. I'll look around at some of the premium prop makers to see what I can find. If all else fails there is a guy in Milford that makes custom props. Pricy ($60) but very nice.
Just a thought - the prop makers would probably be more receptive to making props suited for your engines if they were sure of selling enough of them to justify the set-up cost. If RCV were to offer to buy a reasonable quantity of 3 & 4 blade props they would most likely be willing to make them. RCV could, in turn, offer them for sale to their customers. Once the manufacturers are set up to make them they would soon be available at the normal outlets. I would think this would be in the best interest of all concerned.
RCV would probably sell more engines. The lack of available props is, frankly, a deal breaker. What good is an engine if you can't get a prop? Since the whole purpose of spending the extra money is to enhance the scale appearance of the model, if you can't match it with a scale looking prop the purpose is defeated - you might as well stick with a conventional engine! Additionally, warranty work and the companies reputation for durability would probably be improved. I just got a second-hand RCV60SP that came with the prop the guy was using for break in. It's not the recomended pitch but the heaviest pitch commonly available. I suspect that a good many RCV buyers are doing that. Under pitched props will result in higher revs and probably premature engine failure. That's bad news for everyone!

The prop maker would sell more props since they would be the ONLY manufacturer of props suited to this purpose.
The modeler, your customer, would gain by having engine/prop combos that enhance the scale appearance of their model.
Just a little something for the suggestion box.........
Larry