This is a really smart idea. I took my tray off because I kept banging my damn knees on it. Right now I have it on a roll away stand but when I'm in the standing position on my desk, I can't play. This would be a good remedy to that situation. Which legs did you end up going with?I was thinking and working on a keyboard solution for a lomg time. The problem is always: either the keyboard is too low if its in a drawer under the desk which causes me posture problems working long times or too high and in the way for other work if its on top of the desk.
So my solution is the attached. I modified an electronic desk stand which can be electronically put up and down. Then I attached aluminium profiles and rolls to it. Now if not in use I can roll it deep u der the desk completely out of the way and when I need the master keyboard I pull it and move it up using the remote.