if you have plenty of room I'd go with a full sheet of 3/4 plywood, by the time you get your padding on there I don't think you could warp it with heat, you'd burn your fabric first. just make sure it's well supported or it will warp on it's own. you can get the cabinet units one at a time as you can afford it to go under. that's what I have in my room for cutting (1/2 sheet) and it's the perfect hight, wish I had one for iorning too