I covered the option of extra diodes in my post - this loses some voltage and power.

Such a circuit would allow data logging of generator (rectified) voltage and battery voltage separately.  Together with wind speed this would be useful.

If you can put up with the dreadful TO220 package you have a lot of choice, if you want a decent package the choice is very limited and the cost is high. You don't say anything about your current so I really cant give much more help. For the series diode as you are needing it a 40v device will do.

Yes you can also replace the main bridge with schottky but I don't recommend it. They are rather close on voltage for a 24v system and if for any reason you loose the load you will blow them. If you can guarantee the output will never go open circuit then they will be ok but you will need 100v devices and their volt drop is not so low.

There are significant differences in ordinary diodes but it will make precious little difference to your output ( it will make a big difference to the size of heat sink needed). The potted bridge thingies are convenient but they are not the best choice, they have higher drop and need more heat sinking. Decent individual diodes of the stud mount or pressfit type will give your more current carrying with less heatsink.

In terms of actual output you will see no difference on a 24v system, it may seem rather serious on a test bench with constant speed drive but under wind conditions it will make no detectable difference, at cut in the power from the blades just overcomes the system losses and as soon as the diodes conduct you will just drag the speed down, it will take considerably more wind to give you enough to show a useful charge. ( if you are worried about a few tens of mA then ok, but real charge it makes little difference). Even in high winds the main gain from more efficient diodes comes down to less heat sink, it will not significantly affect the output.

At 12v things are starting to have real effect and schottkys may pay off, but at 24v  I think that in the end conventional diodes will prove just as good and more reliable.

For the same reason I think your interest in volts below cut in is a red herring unless there is something seriously wrong with your cut in speed, there just is no useful power in the lower winds. Use a schottky in series for your tests to check your cut in speed is near ideal, then short the thing out and forget volts below cut in, bearing friction will have more effect than that diode drop.

Your voltages indicated are undefined and the circuit itself is not well determined.

for one include the Fet intrinsic parasitic diode and you will see the differences and limitations.

The V1 voltage will be inserted into the circuit when its voltage is within V2 less 0.6 volts, also the 2N3906 Base Emitter junction is in reverse mode allowing the breakdown ( Zener voltage of it ) flow current causing transistors behavior to be affected.

Then if the V2 voltage is greater by 0.8 volts than the V1 voltage, the Fet intrinsic diode to be turned ON ( reverse mode operation)- which may give you problems if V2 does increase radically.

If you want and really need to measure the voltage at any time, then another circuit is needed, like to be installed up the tower and brought down either with wires or wireless device to send the data.

Proper data taken is BEST to define the generator Volt/RPM and RPM measurements will give you the generated voltage even under any load and if you have the generator internal resistance, then you may be able to calculate the stator watts dissipation at any instant.

One needs to think in practical terms the parameters and the design of a circuit to see if it is applicable for one needs.

From what I understand then, I could use 40V schottkys.  Trawling through a local components store's website, I found:
Model    :    STPS1545CT
Device    :    Schottky
Type    :    Power
Forward Voltage @ Forward Current    :    0.57V
Device Package    :    TO-220AB
Termination    :    Plastic
Repetive Peak Reverse Voltage    :    45V
Max Forward Rectified Current    :    7.5A x 2

But that seems to have a 0.57V drop!?  So not much better than normal diode anyway...unless maybe drop is much less at lower amps.  Any comments appreciated.