Update,
I received my HI-Perf endorsement yesterday. It was painless and now nobody can question the time I Log in the C-310. But as others here have said, you don't need the Hi-Perf endorsement to LOG multi time only to ACT as PIC in the 310. There are a few FAA Letters of Interpretation that address this exact situation and are quite clear on the matter. John Burke's post explained it best.
FYI, the Letters of Interpretation can be found under the questions submitted by. John Speranza and Jason E Herman