I like the idea of rhs with the spacer, nice and neat, you could probably get away with just gluing a closer stip over the angle to keep dirt and chips out.

Where would the ball screws go on the first one? with those rails could you wrap the carridge around the beam and mount the srews and motors on the back or would the leverage be all wrong? not pull ing from the centroid etc...

Some of them are very similar to yours Ross!
I guess there are no new designs its all been done before and when you start leaning out or designing close to the wire you end up at the same point any way. I'm sure I ve seen elements of my design else where and thought if i just change that a bit and move that over there it will work how i want it too.