Brilig-
It is a little late at this point. 1/4" was an approximation in the first place, especially if a cloth layer was added on both sides. On my last suit, I measured 36" down the spine and tail with a yardstick. Rules it off with a permanent marker. Funny thing, it never measured 36" long after that first year. Nowhere near.
But then again...it wasn't Rubatex, either.
The problem is not just "air" or nitrogen blown. I may be out of date on this, but they were never "air blown". Either nitrogen was introduced to the liquid neoprene "batter", and then allowed to foam up as the mold was opened and exterior pressure released--the same as taking the top off a Coke bottle after you shake it--or, the big problem, was that most other material was made at much lower costs by simply mixing up "pancake batter" and letting the various chemicals foam and fizz on their own. Much less control of the process, and no way to tell how the chemicals would affect the rubber in the long term. Cheap caustic chemicals actually do attack the neoprene and break it down as it ages, it isn't just "gas leaking out".
At least, that's how Rubatex explained it to me some long years ago. Maybe by now they can use nanites to excavate the bubbles in the material.(G)