Most excellent, Gary!
One thing I noted, and you might want to reconsider:
The casters are fairly close to the vertical axis of the DP. There's a lot of mass up high...ie the centre of gravity.
Moving the wheels to a point as far away from that as possible (outwards) gives you a much more stable base (safety).
Because they're casters, if the DP starts to tip sideways you won't be able to stop it...the wheels will just accelerate the toppling effect.
Mind you, having the cabinet loaded with weight inside it certainly helps bring the C. of G. down, making the assembly more stable....still(?).
Another way to 'kill the cat' might be to rotate the DP 90 deg., and centre it over the length. The only downside to that would be that the cabinet door would be on the side rather than the front. The good news is that you'd have a much wider base and you'd be able to stand closer to the DP table for accurate measuring etc., should you need to.
I know all of the above because my machinist buddy pointed this out to me regarding my mobile base... *oops*