However, must say these sort of decisions should have been made a long time before you started building the base. If you are taking the design as you build it route then expect a lot of wasted material and design changes.
have most of the design pretty much fixed, however what looks good in CAD does not always translate to the real world, Many things will change as the build takes shape, as i discover the disconnect between Screen and reality.
Y rail position is a fairly easy change at this point.
I have worked on cheek mounted rails as thats how things evolved in CAD but as i start to construct that little devil on my shoulder keeps questioning my decisions.