Hi

Wont be a problem as it will have equaL up forces from the guide underneath

in that drawing, my x would be were moment A is, and were the two yellow arrows are ( d3 ) would be the top and bottom connection to the X Rails.

The Y gantry, will be between the 2 x rails ( above and below ) , putting its COG were moment/force A is. I think i will only need the tool going below the gantry, not the spindle, the aim was always to get the bottom point of the spindle finnishing at the y gantry and bringing any material up to it