5 year medical acceptance in Mexico

My class 3 medical just went over 3 years. Even though its technically
good for 5 years now I'm considering renewing it to avoid confusion in
Mexico. Has anyone on this list had any experience with using a 4 year
old class 3 medical in Mexico? Did they seem to be aware of the
extension?
I've been briefly detained a couple of times because my medical was
issued as a class 2 (which is good for 1 year) but I've been able to
explain to them how it works.

-Robert