Ok. So middle is assmbled. It’s ok, heavy 1382g and RIGID. DO NOT TIGHNED THE SCREWS. Z glides verry nice and xy the same :)).
One little “problem”. If you use Allen or hex screw see the pic (center final 4) with circled areas, if you use Ryan recomended screws disregard this.
The bolt head is too big so you need to cut the bolt head 3mm at 30-40 dgr angle.