I hope I do not confuse the issue here, but I see the 2.5 oz as an administrative standard of the MMMP. That said, the "law" is simply an affirmative defense for an MMMP card holder and specifically does not state limits. For example, if you kill someone in self-defense you have still committed murder. Here self-defense becomes your affirmative defense. The MMMP 2.5oz per patient transport limit guideline is your safest bet, but the police are not going to split hairs over a few grams because they don't have a chance in hell of getting it through the court system.
Hope this helps,
TheMan13