Made of aluminum, Made for aluminum: Would love design critique!

[gamingan]

So, I squeezed in a few hours every night for the last 5-6 days to design this one, using experience from my tiny first machine (moving-bed style for wood) and exploring other people's builds online.

Pretty proud of the effort as a beginner, but not so confident (read: nervous) about how this machine will come out in reality.

I do have some unresolved questions (see further below), so I would definitely appreciate some feedback before I get going!

Below are pictures of the best design that I could manage to create based on:

• my dimensional requirements/constraints
• the goal of cutting aluminum
• taking advantage of at least some components like rails and bearings that I already had lying around

Here are the questions/concerns that I have (Q1, Q2, etc. are marked in red on the first picture above):

• (Q1) Do I absolutely need a support-bearing block for the Z-axis ballscrew? I did this for X and Y, but the Z-axis construction is really tight on space, so I'd prefer to leave it out if that's fine.
  
• (Q2) I presently have two Hiwin HGH-15 bearing blocks for Z-axis; ordering more would add cost and more importantly time due to re-shipment, not to mention the reduced Z travel. Is two bearing blocks good enough?
  
• (Q3) Any improvements I can make on these plates? I used fairly thick plates (15mm), but I'm more concerned about the shape and positioning.
  
• (Q4) Steppers: 350 oz-in. Are these going to struggle with moving the amount of weight all the parts add up to? I am mostly concerned about Y, even though I have dual-drive (i.e., two steppers) on that axis. I don't need too much speed even on rapids, as this is mostly for occasional personal use. I do want the router to run without skipped steps obviously.
  
• (Q5) Any other general feedback on overall structure/geometry? I'm excited to begin assembling this, and see where it goes.