"Mike Rocket J. Squirrel Elliott" wrote:
...
One thing about MDF, etc., in baths I don't like is their propensity to
absorb water (both spilled and humidity) and swell...

Oh. (In Johnny Carson voice): I did not know that. /That's/ a good
reason why I should not have used MDF for this application.

At least MDF is less susceptible than alternatives you could have
chosen...