I really need to get busy building my layout. I have a 9 x 10 foot room, so all I need to do is decide whether to keep the track at "sea level" or have grades. Also, I'm not sure if I should use foam or plywood for the base. In all the decades I've been in model railroading, this is my first real layout. Therefore, I would like to avoid problems if I can. Any comments pro or con to the questions I asked above? Thanks!