RE: Building board question
Here is what I recommend if you are up for having it be heavier and less mobile.
I built myself a mini bench using 3/4" ply and 2 TV dinner tray tables (From world market, theirs were better quality then the ones from walmart)
I went in and attached the Tray tables to the 2'x4' ply using big blind nut type things (they recess into the wood) and bolts. Then I glued on a piece of project board onto the top of the plywood using contact glue. Project board can be gotten at most places you can get wood. It is usually kept over where you can get smaller pre cut pieces of ply. Project board is basically VERY high density non corrugated cardboard. It is very hard and similar to what is used as stylized bathroom walls. It is 1/4" thick in a 2'x4' sheet.
On top of this I glued pieces of 1/4" cork board that I found in the office section of walmart. They come in a package of 4, and each piece is 12" square. I put them side to side and used contact glue here as well. If you want to get rid of the seem, you can then use the cork board roll that you found and put it over it )it is about 1/8" I think). On top of that I put a piece of ceiling tile from the hardware store (you can get single pieces, just ask really nicely).
This might be a bit over kill for you, but it is quite nice to have a (relatively) sturdy table that I can move around as I need. I can remove the tray tables at any time by removing the bolts and then place the board on top of any other table.
total cost:
Tray tables $30 for 2
Ply wood ~$5 for the sheet I think
Project board ~$3
Cork pieces ~$8
Ceiling tile ~$3
Misc hardware ~$6
and then whatever glue you want to use.
If you do it without the tray tables, it is actually a very cheap board that is nice and strong with plenty of depth to sink T-pins into.