I am working on a shaft hub mount I will post here when I get it done also. Crazy weather has me tied up and slowed down :(

The hubs have the center hole large for the adapter I am making and also to kinda keep anyone from trying to use a cheap threaded motor arbor for a shaft mount, those things are not good and will snap off at the threads at times. There may be some better ones made, but the hardware store ones are about junk in my opion and certainly won't work for these 10" size hubs. Just the hubs weigh over l lb 4oz for the 3 blade and I think the 6 or 7 blade was about 2lb 4oz. Very nice solid blade hubs and strong.

The 3 center holes 1/4" are a very good mounting for using a weld on type hub adapter that can be bought at some farm stores if you find the correct size, get the correct bore for the shaft being used (with or without a keyway) and drill/tap the face for the 3 1/4" mounting holes to match the hub.
That is if you want it removable which I do like myself for swapping out blades fast for testing different things.
 With several hubs on hand, you can set up a new set of blades on a hub and have them ready, then just run out and back in the mounting bolts and you swaped out blades in just 2 minutes or less downtime on the genny (or in the rain/snow/sleet or other yuk), depending how you have to get to the genny to swap them. Also save a few dollars needing just one shaft mount per genny.

 For experimenting with several motors and lots of different blade stuff, size, type, number etc.. this is handy and fast as well as not too expensive. One extra spare blade hub would then fit most any motor your flying since the bolt on shaft mount is drilled the same way on each one to match the blade hubs. So no need to have a 6 blade hub for each of 3 different motors as spares just because the shafts are various sizes. Get 1 shaft hub mount for each motor, then use the same 6 blade hub as spare on any motor you have. Then of course you also can use the 6 blade as a 2 3 or 6 as you choose.

Since I change things so much myself here trying new things, I put allot of thought into making these and the above swapping info. In the past I did things the hard way because I did not have any hubs like these, but now that I had them made and making mounts for them life will be much simpler for me when swapping things out for testing.

Course some people might preffer to just get a weld on shaft hub mount and weld it permanant to one blade hub and be done with it.
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nothing to lose

Far too many variables to actaully say. I think in normal use your motor shaft or blades would be more of a limiting factor than the hubs.

Say PVC blades you could make so long they flop like a wet noodle, but won't hurt the hub.

Large or heavy enough wood blades I think the motor shaft would bend as a weak point durring yawing force before anything else would give out. If a person was using real large/heavy wood blades I would use 2 hub plates to prevent any flexing. With a front and rear blade hub and wood blades in between I dought anything close to within reason would ever hurt the hubs.

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nothing to lose

Basic info on those small hubs.

The small one fits inside about a 3.2" circle since the ends are flat.
Arms 1.5" wide, from arm edge to hub center 1.5", hub center to center of outer hole 1.25", small holes 0.135", center hole 0.25"

Larger one fits in 4.125" circle since the ends are flat.
 Arms 2.5" wide, from arm edge to hub center 1.75", small holes 0.185", center hole 0.5"

Sizes could be off slightly, I was planning to re-drill holes later.
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nothing to lose