The thing about "designed for voltage doubler" has to do with shielding the external electrical field. With a full-wave voltage doubler, one terminal of the winding is at AC ground (through the first capacitors) and I put that terminal at the outer end of the high voltage winding so that the outer winding layer acts as a shield. There will be a much larger electric field around the transformer with a fullwave bridge, and small signal circuits with high impedances are likely to pick up some hum from capacitive coupling. This is a lesson we learned from the PT-1 in Seduction, and is the reason for the copper shield around that power transformer. (There is also a magnetic shield tape around the PT-1).
You could use the Eros PC board and drop some voltage by using the Eros shunt regulator. If it were me, I'd jigger the Foreplay a bit to run at the higher voltage (225v) with more current, but you could instead run the shunt reg down to 150v (or 190v, which many Foreplay IIs actually ran at.) The Eros board has a voltage regulator for the heaters. You could also just use a 150v gas regulator tube, as in the stock FP-III.
