RvB is correct that when you put the KAPEX on the floor, the height of the bed is the height of a SYS 1 to allow you to use them as material support (clever idea). But when you put the KAPEX on an MFT KAPEX table, there are extra holes in the top for "registering" the base of the MFT KAPEX that lower the height slightly.
An MFT/3 sits at a working height of 900mm and an MFT KAPEX sits at a height of 790mm, a difference of 110mm. A SYS 1 sits at 112mm high.
Hope that bit makes sense.
The UG extensions are designed to work with the KAPEX bed at a working height of 900mm, so if you put the KAPEX on a MFT/3, the bed would be at a working height of 1012mm or 1010mm if you cut extra holes like in the MFT KAPEX top. At this height, the UG extension legs wouldn't reach the floor.
What you could do though, and what some members have done to increase the height of the MFT 1080 or MFT/3 tables, is to produce a couple of leg inserts to make the legs longer.
Something like...
See
http://festoolownersgroup.com/festool-wish-list/wish-the-mft-had/ for the detail.
I'm just a shade over 6'1" and the ergonomics of the KAPEX on the MFT KAPEX table are good for me. Have you tried using the KAPEX at the two heights to see what suits you?
The UG wings can also be used as material support for the MFT/3, MFT/3-VL and the CMS as they attach to the rails in the same way that they attach to the KAPEX. Obviously all of those have a working height of 900mm to allow them to be used as material support for each other too. Changing the KAPEX height and the height of the UG wings would negate those additional capabilities. If you ever wanted the mobility of the UG cart, then that also operates at the working height of 900mm.
Just some other elements to consider.
