The thing is, i have a primary current sense transformer, to help limit primary current, and at the output there are output inductors.....so the primary current is limited.
i cannot see the primary current being high enough for long enough to charge this series capacitor to above Vin/2 at the most.
It is crucial to get this capacitor as small as possible, since it makes the primary switching loop far easier to lay out.
-also, these low dissipation film capacitors are expensive.