Welcome @mcolin, to the community!
You have probably connected the two capacitors in series to divide the voltage between them so that each sees (approximately) the same voltage, right?
The halving only works with halfway identical capacitors, which is usually guaranteed with the same batch, but should actually be balanced by equalising resistors connected in parallel.
By connecting external circuits such as this flyback converter with VIPER06, however, you would completely confuse this voltage halving and considerably increase the voltage at the upper partial capacitor.
In my opinion, you must connect the flyback to the full voltage. If this voltage is too high, you could select a VIPER with a higher voltage rating or set up a cascode circuit.
Hope that helps?
Regards
/Peter