Ballscrews Z axis

Hi all

Just wanting to pick your collective brains.

I'm building my own custom 3D printer it is a CoreXY design the CoreXY part I have all sorted and tested and I'm happy with that.
I'm now doing the Z Axis, I was planning on supporting the Bed on all 4 corners (smooth-rod) Plus 2 Ballscrews on the sides at a central Point. however after finalising the design of the CoreXY stage I can no longer put the ballscrews at the sides as originally planned!
so I'm now having to do a rethink I can either put one at the front and one at the back of the printer in the middle which will obstruct removing 3d printed parts from the front (but I can still access them from the side) or I could replace two opposite corners with ballscrews
so that would be ballscrew then smooth-rod at the back and smooth-rod and ballscrew at the front or the last option is to just use one ballscrew at the back.

what would you do ?