saramos,
I use the same system. Originally I had a hollow core door which I put ceiling tile on top of to pin too. But then I built the [link=http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/tools/magnetic_building_board/index.htm]magnetic building board system at www.Airfieldmodels.com[/link] and I won't ever use anything else again. I have 3 sizes of steel sheets I use, the main building area is 24"x72" and I have 2 smaller sizes I use for building smaller components on, 12"x36" and 12"x24". This is by far the easiest, fastest, and best way I have found for building planes. It does take a bit of time to get it set up and may be a little expensive for some (total cost on my system was approx $250), but IMHO it's well worth it.

that's my 2¢ worth.

Ken