Just to clarify a few confusing issues:
When we have DC filament power, it has always come from Schottky rectification. That includes the Seduction, of course.
The Seduction uses UF4007 diodes, which are of the so-called "ultrafast soft recovery" type. That means the reverse recovery spike is very short and relatively small. These diodes can be easily replaced by the 600-volt IXYS silicon carbide Schottky diodes that we use in other products; they are quite inexpensive.
The RRSF (reverse recovery spike filter) in the Seduction is a CRC filter between the transformer and the diodes, which reduces or eliminates ringing in the transformer caused by the reverse recovery spike. We tried several approaches back in the day, and this one was the most effective.
A low-ESR capacitor will not reduce the reverse recovery spike energy, because is has no energy dissipation mechanism. Snubbers are usually designed with a capacitor in series with a resistor; the capacitor makes the spike longer and shallower, and the resistor absorbs its energy. It's mostly the total energy that causes the transformer to ring. The cheap mylar capacitors have significant ESR at the very high frequencies characteristic of the spike, so they don't need the separate resistor.
Technically speaking, Schottky diodes are NOT "soft recovery" - they have no recovery at all, soft or hard.