From John Lynch (FAA big cheese) per an email to me dated 10/5/2004:
3. The person must have logged at least 5 hours PIC flight time in a Cessna 310."
61.195(f) Training received in a multiengine airplane, a helicopter, or a
powered-lift. A flight instructor may not give training required for the
issuance of a certificate or rating in a multiengine airplane, a
helicopter, or a powered-lift unless that flight instructor has at least
5 flight hours of pilot-in-command time in the specific make and model
of multiengine airplane, helicopter, or powered-lift, as appropriate.
I have previously assumed that an IPC doesn't fall under "required for the issuance of a certificate or rating." Did your source explain this?