Mine is made of particle board with Posterboard covering it. I don't use T pins.

If you are using a balsa board, cover it with something like posterboard or something like that. You can still push pins in if you want, but won't ruin the surface with glue. I would think that would be too soft of a surface. Spill anything on it and it is no longer flat, be it water or glue. Glue won't come off it very easy without chipping it up bad.