If you are worried about a foot or two then at what point in the aircraft the actual static pressure is detected by the altimeter is important.
Is it at the entrance to the static vent on the side of the fuselage or at the actual instrument?
You may find that you are even lower than you think you are if the instrument is 5 feet above the bottom of the fuselage and the pressure is detected at the instrument
I'll get my coat...