I am busy assembling an Openbuilds C-Beam XL machine according to a manual I downloaded from Openbuilds, The issue I have relates to the 1000mm C-Beams and the V-Slot. The manual says to ensure all are square and equal in length. Once that is achieved one must then cut 40mm off each of them (tight fit) or 41mm (easy fit). Why is this necessary? Can one not just use the full 1000mm length? Does the V-Slot beam need to be exactly the same length as the the 2 x 1000mm C-Beam lengths? Thank you.