Yes 30 ohms is the figure I have always been told is the Koetsu ideal. I have tried 30 ohms in the past and found it a bit shouty.
I am very curious also. 
Oh, what resistors work well in this scenario?
There seems to be as many foo resistors as capacitors.
It’s a subjective thing, so regardless of what the manufacturer says, use what you prefer. The AN silver tantalum are great, though expensive. Lots of folks like the Vishay foil, available from Charcroft/Texas in custom values.
Yeah, trouble with subjective is you don’t know what you’re happy with until you’ve tried everything possible. Being indecisive I’m never sure that I’m happy at the best of times. Thanks for the resistor recommendations. If I put loading on the primary do I need to reduce the value by dividing in by the turns ratio squared?
Yes, for primary loading, it’s just the value of the resistor in parallel with the reflected load (47k/turns^2).
a comparison between 3 inputs of my SUT - 2.5, 10 and 40ohm - clearly shows 40ohm a preferred one.
Pete,
Is it possible to generalise on the difference sonically between the Charcrofts (have them in my Paradise Phono stage) and the AN silver tants if I fancied a bit of a play about? Charcrofts seem very clear and dynamic.
I’ve not compared directly, but from playing with these things in various circuits I would say the standard tants are very sweet and the silvers add a good dose of resolution. The Vishay have essentially no discernible character.
Cheers Pete,
So the silver tants will add a bit of sweetness with the same resolution as the Charcrofts and the ordinary AN tants will add more sweetness but less resolution?
Might look into this at some point.
Well, these are just my general impressions, so caveat emptor. In general vishay=less character, while AN tant=more.