Wow. Thank you all for your responses. It's like sitting in the cafeteria at school.
No choice now, I am going to crack the case and have a look for that elusive center connection, but will also test the partial connections option and take some readings. I have a crude MG test set available to put this gennie through the various wiring configurations. It uses a series of baseboard heaters as the load.
First, some replies to the questions that came up:
For Coldspot; C/2C is short-hand for converting a three phase motor to a one-phase generator with capacitors. As mentioned in the replies to my question, you put capacitance in parallel with two of the three windings and take your power off one of them. One capacitor on the first winding, twice that on the second, and none on the third.
For Flux; I'm stuck with 240VAC/60HZ because one the of the users runs directly off the plant at night. I've advised against it, but it's worked reasonably well for him the last 15 years or so. A current monitor blows the other 2 users off the system when he draws more than 100W. They're on chargers so they get their power when he goes to bed.
For Nando; I'm currently running a 1800RPM unit at a location that now has a relocated intake with less head. The 1200RPM unit will avoid the need for some drastic pulley ratios. My concern about overheating/eddy currents revolved (pun intended)around the fact that the unconnected Y circuits might negatively affect their neighbour coils even though they were not connected (or vice versa) through induction or whatever.
If you can stand it, I have one more question...
Is it possible to use the Y and D connections in parallel (properly phased of course)? This would be a fall-back if the center point is not accessible. Nando alludes to it, but I may be misreading things.
Rob