It does make sense to space them out with regards to resonance. This is the reason I wanted a second opinion, thank you. The z travel is only 90mm now. I was going to go for a longer travel but decided to keep it simple for a first build. Squareness shouldn't really be an issue as the t slot nuts can be moved/adjusted then tightened so that doesn't really concern me. As I said before, high resolution finishes are not my main goal(I'll be building furniture mainly), but a certain degree is essential. For cable management I'll simply be using a piece of angle aluminium on the back of y with a train on it. There are a lot of items I'll be using that are not on the drawing just yet. I think the biggest mistake was ordering parts before I was completely finished with the design so it kind of limits my adjustments now. Oh well, you live you learn. Nothing that can't be sorted. The cad software is Rhino 5