So, when an animal with Cunning becomes a familiar, it gets an Intelligence of -3. Per the Form guidelines for Animal, since the familiar now has Intelligence, a maga would use Mentem to affect its mind, not Animal. But that still leaves a question -- to what levels can those characteristics be raised?
For example, an average crow (using the qualities and stats from HoH:MC) has mental stats of Cun 0, Per +3, Pre -1, and Com +1. After being made a familiar, it now has Int -3. So, are the maximum stats it can be raised to with CrMe:
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Int +2, Per +8, Pre +4, Com +6, where each is an average crow-turned-familiar +5, following the CrAn guideline of no more than 5 higher than an average for that kind of animal;
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Int +5, Per +8, Pre +4, Com +6, as above, but we use the pre-familiar crow's Cun 0 as the base for the familiar's maximum Int;
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Int +5, Per +5, Pre +5, Com +5, following the CrMe limits for a person;
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Int +5, Per +8, Pre +5, Com +6, using the higher of the CrAn and CrMe limits; or
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Int +2 (or possibly +5, from the Cun 0 base), Per +5, Pre +4, Com +5, using the lower of the CrAn and CrMe limits.
(I note that if the answer is #3, you effectively get #4 if the maga raises a to-be-familiar's start-above-0 mental stats five points with CrAn first, and then, after binding, raises the other stats to the limits of CrMe.)