Looks like a clever design and use of space. I'm not sure you'll see too much speed benefit from the R&P over 5 start screws for a machine this small -- it does take time for any mechanical system to accelerate. Still, it should be somewhat faster for larger pieces.
It looks like you have a good handle on things -- really nice work in CAD. My only advice is that if you think you want to build parts that are 22 x 34, you go larger by at least 4 inches, and preferrably 6. Keep in mind that you need to take into account cutter offsets. Additionally, it's annoying while you're jogging around to keep running into limits, and this will happen often if you're trying to locate off the edge of stock for a large part.