ok, first attempt using sketchup 8

[JAZZCNC]

Right taken on board what Jazz has suggested and more or less gone back to my earlier design. Instead of 2 steppers on the X, i will use 3 belts and 1 stepper

Just the sides would have been enough.? How wide is this machine.? Looks wide so I'll warn you belts this wide are not easily found and you may have to get them custom made.? I did and my machine looks narrower than yours.!
Has much as I don't like slaved steppers I have to say at this width then they may be a better option,! And despite having to tune them slightly slower to stop stalling/racking then With 10mm pitch screws you'll still get decent speeds for cutting wood so shouldn't be too much of an issue.! . . If your feeling flush with cash Buy some of the lead-shine digital drives and you can even be protected from racking if you take advantage of the anti-stall feature built into them.!

While I'm here and commenting then got to say not keen on the Z axis setup either.? your putting all the weight of the stepper and screw with it's bearing blocks on the front plate.??
Looks like you have plenty of length to the back plate to switch them round putting screw and motors on the moving y axis so just ball-nut is attached to front plate. The Z axis then only has to lift it's own weight plus spindle so higher acceleration can be achieved. Higher Acceleration is very handy on the Z axis esp when it comes to 3D work or V carving etc.

Sorry to keep throwing curved balls but you keep sticking your head up .. .Lol