"Doing this I should be able to place the low values and/or the high values on a favourable point in the range (that is, in relation to my subject). It should be predictable that way whether I use the whole ten zones, or just part of it. "
The Zone System, when used to its true purpose and benefit, works so that you can do what you want to do with the luminances you are photographing, on a shot-by-shot basis. It was designed with an aesthetic end, not a technical one. The technique of it is simply a means to this aesthetic end. Please do not get stuck in the rut of thinking that every print must "use the whole ten zones," that certain parts of the composition must be placed "favourabl[y]" by anyone's definition of the word but your own, or that what is favorable for one shot is universally favorable for all shots. The perfect negative is simply the one that allows you to make the print closest to the print that you want, not the negative that satisfies some universal and absolute definition of what a negative and a print ought to look like. The Zone System is a tool (and just one of many tools) to let you make your print look like you want it to look, not a guide or a set of rules that tells you what to make your prints look like. It is a misused technical exercise without the human heart and brain behind it to employ it in order to obtain ones specific aesthetic goals – to make an aesthetic decision about ones work, and use the tools at ones disposal to follow this decision through to a successful end. Once you start using the Zone System simply to achieve the technical end of making every negative match a predetermined standard for negatives, you have entirely lost sight of its purpose, and it is no different in results than using an incident meter combined with an eye for luminance range, and blanket over-or-under-exposing and over-or-under-developing.
To use your meter for the Zone System is simple, as it should be. IMHO, once the Zone System becomes complicated (which all those digital features and buttons can help it to do), it has lost its usefulness and strayed far from its original intent. With some experience, you'd do better off using incident meters and educated guesses than you would be fiddling with a bunch of gizmos that remember this and that and tell you how to do this and that. With the Zone System, K.I.S.S. is key. What you do is meter anything. The meter tells you how to expose if you want that thing to be middle grey. If you don't want it to be middle grey, you use a different exposure to make it either darker or lighter. Once you have "placed" that tone, you measure others to see where they "fall." If they do not fall where you want them to fall, you alter development (and sometimes alter exposure again) so that they do.