Just my very subjective estimates from VSA models I've tried firsthand (area and minimum listening distance/extreme nearfield - optimum listening distance)
VR-1 -10sqm- 4 feet - 6 feet
Unifield 1 - 10sqm - 4 feet - 6 feet
VR-2 - 20sqm - 6 feet - 8 feet
VR-4jr - 20sqm - 6 feet - 9 feet
Unifield 3 -20sqm - 6 feet - 8 feet
VR-4 HSEs and SRs - 25sqm - 7 feet - 10 feet
VR-5 SE and Anniversary - 25sqm -7 feet - 10 feet
VR-9 SE - 30sqm - 9 feet - 12 feet
VR-11 SE - 50sqm - 12 feet- 15 feet
If you'll notice, my observations are dependent on first the closest you can listen with the speaker remaining coherent and then given some allowance for space around them given each particular model's pattern and physical size.
I find that the flat off axis response of VS speakers makes me require far less toe in than is usual. This results in configurations that are not equilateral. So in the case of the SRs for example, they could be 7 feet apart and generally I'd be 8 feet from either speaker or at 8 feet apart, 9 to 10 feet away.
Again this is just my subjective take on he question. I prefer a more enveloping soundscape that makes use of room reflections. YMMV.
