Dave Platt AKA Mr. scale uses 1/2 sheet of glass for building board. He believes that you glass top always stay flat, no chemicals or moisture harm it and cleans easy with single edge razor blade and a wipe. You can draw lines on it He uses a tack of CA instead of pins or lead weights for holding things down.
I bought a 2.5x6 feet 1/4 inch glass for $80 (could not afford 1/2) and gave a try and got to tell you I love it, no more warped wings for this guy . Last week I was at city dump and in the aluminum section of recycles they had these beautiful panel doors and windows with 1/2 inch tempered glass intact. You can guess the rest, well a good first place to look.