I'm planning on making this for a single bed. The beds I have are usually up against a wall so I don't need to make it very wide. At first I thought of having it seven blocks across, which would make it 56 inches wide (the blocks will finish at 8 inches square.) A single bed has a 39 inch mattress so that doesn't really give it much of a hangover. I may just add another row to bring it up to 64 inches across. I'll see what it looks like once I get enough blocks for the length.
Have a great weekend. I have Christmas bazaars to attend and perhaps some decorating to do.