Hi PAF, it is a very simple design, but I like that it keeps the gimbal stable, while the store bought stands where the gimbal hangs, allows it to swing like a pendulum. The problem with me giving dimensions are that the three base pieces are based on the width of the handles on the gimbal.

But this might help. You need 2 x 24" pvc, you can buy these pre-cut.
2 x end caps, 2 x 45 degree angles, 2 x T's.
I had two left over 7" carbon fiber pieces, I slid these over my uprights and that's what holds the handles at the right height.

Cut one 24" piece in half, those will be your 12" uprights.
The five pieces for the base are:
4 @ 5 1/2", you can put those together, you will have two pieces now, a 5/12, t, 51/2".
Now put one 12" piece in each t.

You can refer to the pics I provided.

http://wjfieldsphotography.smugmug.com/Other/Shit/n-KJsdM/i-k6Z7X8D

This part will be different for your rig. But you can figure it out like this.

My handles are 16 1/2" center to center, and my back or center piece for my base is 6".

So for instance if you handles are 18" center to center you can just add 1 1/2" to your center piece.

Hope this helps.

Then the back piece on the base is 6"

Just double check you measurements on your handle.