I made a set of big blades to start out with.  The biggest problem I found was that they were high on torque, but low on rpm.  I had a 1 hp pm motor to use as a generator and I couldn't get it to slow the blades down, even when I shorted the leads together. Part of this was due to the torque available, but most of it was due to the low rpms available (low volts).

The bigger the scale, the more expensive experimentation is.

This may be heresy, but I'm a firm believer that in order to adequately test what blades can do you need a big enough genny to (almost) stall them at maximum current draw (others might not agree).

You might think about scaling down the blades to test the geometry.  If you're determined to use the big blades, you might look at converting a BIG ac motor with NeFeB magnets on the armature.  This is reasonably cheap and there's another posting here where an ac motor conversion is getting 12v with only 20 rpm (I don't remember the amps, and I think I'll loose what I've written if I go back now).

Good Luck,

-Dan M