[Arran]

No you don't want to run it with a higher B+ voltage coming out of the rectifier, remember that these are battery tubes so the filaments will be running off that same higher B+ voltage. It will take some figuring to come up with a resistor value but the drop across the silicon diode will be quite a bit less less, like under a volt, just to make sure the replacement doesn't fail I would use a 3 amp diode. In fact you could use a few of those, or some Zener diodes, across the filament string to bring the A+ voltage down rather then adding a resistor, again more figuring.
Regards
Arran