Hey Jerry,
you find this out when you look at motor 3 settings: If ‘min-soft-limit’ is -133 mm (-5.2362") then you have the Z-16 slider. On the new Z-20 slider it is -163 mm.
My first idea was to use two 100 x 60 x 1.5 mm steel profiles with the length of the two Y rails and place them directly under the rails, from front to end, one on each side, and to put this on some base. This has much more stability as just riser blocks under the feet. But for maximum stability and versatility I decided that I will weld a U-shaped base (in the future, will show when ready).
Image: The Onefinity CNC machine’s foot.
A Onefinity CNC mounted on extruded aluminium profiles can be seen here, here and here.
Welcome to the forum!