Hi Ian, ahh the joys of balsa assembly your'e going to have so much fun even with a few rude words thrown in occasionally, I have in the past used mdf with cork tiles with some success although it was not a large board. I was fortunate some years ago, when I visited a model shop while on holiday, to buy a balsa building board 4 feet in length, been using it ever since.
I know what you mean about cabin fever, I have a sever twitch myself.
Mike