If you order a spinner direct from Tru-Turn, and tell them what you plan to use for a prop, they will cut the slots for you. But cutting prop slots isn't difficult. Some plastic spinners have alignment pins that get in the way. SIG spinners have plenty of room so that I can get a slot in a 2" spinner that will accommodate a APC 12.25-3.75. And for metal spinners, I use Great Planes spinners and cut them as needed. The trick is to only cut one side of the slot. I usually leave the front edge alone, and draw in the back portion as I see that I need it. I cut to that line and check for fit as best I can. If satisfactory, I make a paper pattern of this shape, and lay it over the opposite slot and mark as required, then cut to the line again. I make sure there is a little wiggle room for wood props aren't strained nor the spinners get stressed. If it's a metal spinner, you can use one of those Great Planes magnetic balance rigs to check it out and trim as needed. On a plastic spinner, you can just measure and cut carefully and hope for the best. And on either type of spinner, I rarely use a Dremmel tool. I use a sharp knife and file on plastic, and a good file on aluminum spinners. It's a lot easier to control how much you are taking off.
  Type at you later,
  Dan McEntee

Thanks Dan. What you are describing is what I have been doing for years, and would like to avoid if possible. I mostly use Brodak alum or Great Planes plastic nose/alum backplate spinners and they seem to work fine when modified as we do, but still would like a more precisely made product (i.e. from a factory). The fact that APC props don't fit any of the available spinners must have been noticed by someone other than the two of us. Maybe APC would like to start 3D printing a usable spinner that fits their props? Or Howard Rush?

I think that one Howard Rush is enough, we dont need to start 3D printing replicas of him. Ohh on second thoughts a replica Howard Robot might be useful in the shop when I need some Technical genius.

Hi Mike, I usually go the grind and file route but Tru-Turn does have an off the shelf spinner with wide slots that works great for the APC 12.25 x.3.75 or 11.5 x4 (what I use) props. I only have one but have used it on a number of planes with success. It should be listed on their online catalog. 

A few bits of say 1/8 ( ply ? ) and a scraper ( knife )
if you have no virneer .

A few marks Ea Side - same ( as they say ) ,

SO youve a grid or referance , though its NOT the ' Final Posn . '

As in you sit it flat and if youve say 1/8 or 3 /32 ply ' even ' off cuts , use the scalple to set parralel lines aft ? of ea cut out ( in rotation )

Then holdin a ' thing ' thru the prop cut outs , across the spinner , staring at the base , you can mark even steps round ways , using Yr packers .

Hope thats readable logically . Obviously you need virgin cut outs , or one edge at least . SO IF THEYRE EVEN , Theyre In Balance .

Which is why & what . i.e. a grid where youll whittle the spinner .