I put an additional 8.5VAC winding on my toroidal core transformer in order to increase the voltage so 30VDC could be delivered. Because the heat generated at worst case, which is a shorted output and full current, was far to heavy to dissipate with my little heat sink, the additional winding is switched off when the temperature gets too high. This is done by a simple PTC-based comparative circuit with a relais output. I just changed a few things to achieve that the comparator can't reset itself, but requests a push button.
I wanted to go all the way and tried to switch off the "bigger" original winding instead, but apparentely the voltage was too low so the circuit for the negative voltage stopped working. Without the negative supply, the project did act quite unstable and could not be adjusted.
Of course, your smallest voltage is higher than mine, but I just want you to know that there's a limit. Can't say for sure how low you can go, though.
There is also a moment of output instability when the switching back to full voltage occurs. I think it has something to do with C1.
Do you intend to switch the windings automatically? Your 31.9V could be just a little to less. Depending on your transformer, you could perhaps put windings in series. The current is a little low, too.
