I built something very similar too. My setup is to have two screens, one for standing, one for sitting (and two set of input devices). I close one screen when I'm using the other and I mirror the image on both screens.

I have another setup with an Ergotron Workfit (can be lifted up and down) but I find that the position is more adjustable with my mirror-screen version. With the Ergotron the position of the hands relative to screen is fixed so eye-screen distance can't be adjusted as well as I'd like. Also screen height doesn't go as high as I'd like.