I am trying to do a fairly low-key B&W image with my 5x7 camera - it is of some orange-ish flowers in front of a black board, using light from a north-facing window and about a 2:1 magnification (i.e., the flowers on the ground glass are twice as large as in real life). If I spot meter off of the black board, the meter reads 60s @ f/64 which would give me 30s @ f/32 (my desired aperture for depth of field) for middle gray since I am adding 3 stops of light to get from Zone II to V. If I meter off a gray card, I get 30s @ f/32, so that is easy - however, I also need to add 3-stops due to bellow extensions, which gets me to 2m @ f/32 which translates into 12m @ f/32 once reciprocity failure is accounted for (I am using the formula from Way Beyond Monochrome to get the final number). I realize that I will need to do N-2 development to prevent too much contrast.

However, thinking about this last night, I realized that reciprocity adjustments are there to maintain shadow detail, something that my still life has almost none. I want a pure black background (with no detail) but it is the flowers (on Zone VII) that are important. I am worried that even with the N-2 development, I will not have sufficient detail in the leaves since the highlights are building up so much more due to the long exposure. How much past Zone VII will the exposure push the leaves? IX? X? XI? In all three scenarios, an N-2 development will not give sufficient detail to these highlights. Should I perhaps shoot the flowers as Zone V, let the exposure push them to IX and then N-2 to bring them back to VII? Perhaps underexpose the negative, sacrificing the minute amount of shadow detail to prevent highlight blocking up? Or should I use a 1:100 Rodinal semi-stand development to control these highlights as opposed to D-76 1:1 in a rotary processor, which is my normal method?

I hope I am making myself clear - what is the best way of ensuring my highlights are Zone VII given the lengthy exposure necessary?

Lastly, I am somewhat guessing at the depth of field as the image on the ground glass is way too dark for me to make out, even with a loupe and a flashlight shining on the flowers (this light source will not be part of the final image). At f/5.6, I focused on the front flower, focused on the rear petal, adjusted the focus between the two and stopped down to f/32. Is there a better way of doing this?