Yeah, but the only way you can get constant voltage sources to behave is to connect them in series (and BTW, still only one FWB is needed). That's twice the voltage he needs.
If, between the four windings you have, two pair of them match (most likely pairs on the same toroid, but in case those aren't well matched, try against the other toroid's windings as well), you can connect them in parallel. The voltages need to be very well matched, otherwise 1. the higher voltage winding will force a current through the lower winding (the voltages subtract, putting the difference across the winding resistance), effectively a shorted turn of some magnitude; 2. the higher voltage winding will also source more current than the other, since to draw any positive current from the lower voltage winding, you must first subtract the current being forced *into* it by the higher winding. At this point, the higher winding has approx. double the idle current flowing, while the lower winding has null current!
For loads several times greater than the shorting current, current draw is effectively shared. There will always be some shorting current consumed whenever you parallel the best matched transformers; the matter is determining if the magnitude is large enough to be of concern.
Tim
)