It is possible to make a flyback SMPS with several ouputs both with primary side(with auxiliary winding) regulation and secondary side (with Ref+Opto).
the output voltages of several winding will track the voltage which the feedback signal was taken; the regulation is better than 10% for awell designed transformer. the fromula is as followiing:
Vout
=N(out.n)*((Vout(Aux)+Vdiode)/N(Aux))
thus all output voltage will track the voltage of Auxiliary winding with a simple winding ratio and this is all we need in multi-output SMPS design!
for more info refer to:
h**p://www.powerint.com/PDFFiles/an22.pdf
BEST!