K&M 18811 White

Bought this along with the white 18810 base to hold a Motif XF on top of a Montage 8. Unfortunately the 18811 blocks some functionality of the Montage when installed (foot switch ports get covered) which I hadn't thought about. Installing the unit slightly to the right from the left side will alleviate this issue to an extent, but has the possibility of making a 61- or 73/76-key instrument feel a little wobbly on the left side unless positioned more to the right (possibly making playing and programming slightly more difficult).
Make sure you take into account what will be blocked from the instrument on the first tier and if there's a possibility to allow the first tier instrument to be slightly moved towards the player a bit to avoid that. With the Montage 8, there was a slight increase in wobble when doing just that.

The 18811 itself is sturdy, can carry up to 25kg and is easy to install. Adjusting is a bit of pain and the angles you have available to you are quite limited. There's not much support depth without the additional long support arms (ordered separately) so adding a third tier would limit your instrument selection to an extent.

I got these together with the K&M 18810 White. As with the main stand, the quality of these upper bars, the look, stability and flexibility are outstanding.
The only minor gripe with these is, one of the screws it came with is too long to be tighten properly. It didn't prevent me from using it, but it stood out as a minor fault in an otherwise excellent product.
I would definitely buy it again.