This configuration dciolek is talking about with 12" rotors and 2" round mags will work and make juice. How efficient it will be is another matter. If you don't mind burning up some rotor torque in heat and parasitic losses right in the generator you can do anything and still get juice down the tower and a proper match to the blades. If you want to convert more of that rotor torque to juice then you need a different configuration and you'll still get a proper match to the blades.
I think you have a misconception here Chris. With that arrangement, 12" rotors, 12 2" round magnets, the efficiency is pretty much related to the resistance of the copper and nothing else. There are absolutely no parasitic losses. I find that I can use the same stator exactly that I would use with 1" x 2" blocks, with the larger disk magnets and the power output (or open voltage) at any rpm is pretty much just related to the increased surface area of the magnet. Slightly less, for two reasons I think - 1, there is slightly leakage from pole to pole because the edges of the disk magnets are a bit close to one another, and 2 - the inner windings of the coils are too small to couple all of the flux from magnets this size. But it is surprisingly close. That said, I totally agree that larger rotors with those magnets will get you more power - at the cost of more steel, and more copper. (if you don't use more copper though t he increase will be very small)
My main point here though is you are telling folks that parasitic currents exist in this situation, it is not the case.
To pack the highest copper density in the stator I prefer wedge mags - the reason being is because you're laying things out in segments of a circle and that's what wedge mags are. When I feel like compromising I use bar mags. Round mags are my last choice and in this case require generator rotors with at least 14" diameter to get it even close to right.
I obviously have to agree, wedge shaped magnets are the best choice if your concern is about squeezing the most power from a machine of given diameter.
The only reason round mags work is because they got sheer brute area allowing you to use less turns in the coils. But get them too close together on 12" rotors and you'll be exciting enough coils at the same time - in different phases - to have no problem melting ice off the stator in the winter time, assuming the rotor can make enough torque to get it turning.
It does make me wonder how many different configurations of alternator you actually have built - you seem to think that there is some drag / parasitic losses in this situation, and again, there isn't
If you actually pack your magnets too close together, such that there are times when you actually have two poles over the same leg of a coil at the same time - it will make a slightly funny wave form, however there will be no drag and no parasitic currents within the coil. (I've taken this to extremes in some cases) - it will not make the machine hard to start, it will not cause it to run hot. In fact, if your concern is to get absolutely the most power and /or the highest efficiency from a machine of given diameter (at the cost of spending a bit more on magnets) then I should say pack the biggest magnets you can as close together as possible. At some point it does get silly though. When I pack 12 2" disk magnets onto a 12" diameter rotor - I am having some very slight flux leakage from pole to pole which is not ideal - but it is small and the resulting alternator is still too powerful for the 10' blades we usually fit to it. The sine wave produced from that alternator is about as perfect as my eye can see and so long as they are wired in star... the only 'drag' on the machine is that from the bearings.
Someday... if you like, come by and turn one - and you'll see! And watch my listeroid run at 2kW sustained output. Look at the sine wave and feel how cool the stator runs.
I guess it all depends on what you want in the end.
It really is all a compromise between keeping things compact (and making the best use of steel/resin), making the best use of magnetic material, making the best use of your copper, keeping it fairly easy to manufacture and matching the alternator to the blades. Alternator efficiency is also important - again though, in this case... the efficiency is still related to little more than the resistance of the copper, and parasitic currents do not exist.