Here's the thing. There is probably nothing regarding tube amps that is more confusing and/or ambiguous than the capacitance rating for a rectifier tube. And if you want to play it safe, just stick with the manufactures suggestion, there is nothing wrong with that. But, for me (and to be clear this is JMO/FWIW/YMMV and any other disclaimer you can think of) that isn't the right spec to look at. The spec I look at is the maximum plate current, which makes a lot more sense to me than basing everything off the value of a capacitor, although in theory the 2 numbers are related.

I've looked at this for my UFOs, if you have different amps you'll have to draw your own conclusions. Steve says the power supply cap is 47 uF and the current draw is less than 70 mA. Compare that to some rectifiers per my RCA tube manual:

5U4:  40 uF 1000 mA
5R4:   20 uF 715 mA
5V4:   10 uF 525 mA
5Y3:   20 uF 440 mA

Even though none of those is rated for a 47 uF cap I used all of those rectifiers in my UFOs with no issues at all, because (I believe) my little UFOs never approach the maximum current. The ultimate example of this is perhaps the "ultimate" 5U4 type tube, the legendary WE 422A. According to the data sheet the values for it are 10 uF and 4 Amps (!!!). Some people see the 10 uF spec and say no way would I risk a crazy expensive tube in an amp with a 47 uF cap. If it were me (and to be clear, I've never even seen a 422A, although I'd love to hear them in my system) I look at the 4 Amp spec and say it will probably last forever in my amps.

So there you go. I don't know if this helps, it may very well have made things worse.