One reason that you won't find advice like that from knowledgeable sources is that the ORTF technique was worked out with small, single-diaphragm cardioids, and really requires that type of transducer to work well. Large-diaphragm and/or dual-diaphragm microphones have off-axis frequency response characteristics that vary too greatly from their on-axis response.
The large diaphragm causes the high-frequency response to roll off too much as you get away from 0 degrees--while with dual-diaphragm cardioids, the sensitivity at low frequencies conversely fails to roll off as a cardioid should do off axis. This causes high frequencies to be under-represented for sources close to center, while the sense of spaciousness is decreased by the near-mono character of the low-frequency pickup. All in all, not a good deal.
If you must use large- and/or dual-diaphragm microphones for closely-spaced stereo pickup, it's probably better to set them to patterns other than cardioid. Wide cardioid, supercardioid/hypercardioid, figure-8--try them all. One real advantage of this type of microphone, for example, is the low-frequency response available in the higher-directivity pattern settings, which often exceeds what is available with small single-diaphragm capsules. If a Blumlein setup works for you, try that, or perhaps closely-spaced super- or hypercardioids.