Responsive Photoshop canvas download

Does anybody use just a single Photoshop file when designing all responsive views of a page? I thought i'd give it a go on an upcoming project so I've created this PSD with the 4 different grids I'm going to be designing to.

I expect the PSD file size will get so big that this won't be realistic but I'll report back with how I get on!

If anybody else wants to take a look I've attached the PSD.