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Walter --
You're welcome, and I'm delighted to hear that BTZS has made your life easier! Regrettably, you also seem to be right on target with your observation that "A discussion Forum for something as effective, straight forward and simple as BTZS promises to be a seldom utilized site." I think that lack of chatter here is due to the facts that (1) people who are using BTZS are happily working and don't need to discuss technical problems; and (2) people who are not using BTZS don't realize what they're missing and aren't interested in investigating. Some of them may also be frightened away by the suspicion that this is all about numbers and graphs.
I wish I could think of some way to interest more photographers because letters like yours (and I've received dozens of them) prove that the system is comprehensible and it works.
Regarding Rodinal, and similar highly-concentrated formulas (including HC-110 but excluding PMK), have relatively limited development latitude. You're on the right track, I think, with the idea of varying dilution to control the useful contrast range but these developers are inherently not very flexible. Xtol represents the other extreme with exceptional development latitude. It works well with HP5 but it comes with a couple of drawbacks for some other films, including TMY; very low-contrast development results in excessive speed loss, and (once it gets going) Xtol builds contrast so rapidly that timing is unusually critical.
If you're inclined to experiment further, I'd suggest Ilford's DD-X as being a fine compromise. It preserves good film speed, has good latitude, and can be adjusted to work with about any film by varying dilution. It's also a convenient liquid concentrate with a very good shelf life. Its gradation is similar to D-76's but with a tad less shoulder rolloff. A good starting dilution for TMY is 1+6; 1+5 is better for HP5 Plus.
The notion that middle values can be manipulated by altering dilution contains just a tiny germ of validity because significant dilution changes can sometimes result in discernible changes in curve contour. But that's only one, relatively very minor gradation influence, and certainly not a reliable control or a very useful one.
Thanks for the testimonial; it's good to hear from satisfied BTZSers!
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