Right, the gantry is moving along nicely - i'm at the stage now where i'm starting to add the Z-axis. Its probably time to finalize rail/leadscrew choices before I go much further.

My thoughts have been
X - SB20 rail with 2x 1605 screw
Y - SB20 rail with 1605 screw
Z - SB16 rail with 1605 screw

I've seen mentions of clearance issues/fiddlyness when using SB16 with, I assume 1605 screws...should I just use SB20 for Z as well?
All axis will have a single Nema 23 motor & be driven by belts/pinions. Initial power setup will only be 24V - but I plan on upgrading this to at least 48V in the relatively near future.

Does this sound ok?...what about the Z axis setup?