Thanks for the response. I have no problem understanding what you are saying or the info in the links.
I also realize that if I use a 6k6 that I am running it beyond its rated plate voltage. That said part of the rational of this design is that it is suited to various output tubes per Dave Hunter. I have not calculated load lines for the various tubes suggested but have tried some substitutes and found the results interesting.
Perhaps in the future I will take the time to do the calcs and see just what that reveals but in the meantime I am still interested in others experience with alternative tubes in this design.
For the record I am using the C8r and C10r as recommended in the book. I also have an Eminence Mavrick and a vintage Wilder 12 available. Although speakers do vary a bit I would be surprised if it was apparent in a side by side test. I suspect the amount of break in is probably much more apparent.
As for the B+ reduction the Zeiner approach is perhaps more elegant, I am ok with using resistors and accepting a bit more sag and resulting compression. Perhaps it would be interesting to try the other approach just to feel the difference. Another option is to use the lower voltage taps in the transformer which is probably a better approach than the Zeiners.