-I believe for a beginner is more difficult to mount properly the rails on the gantry if they are not on one plane, precision wise

-its ugly the motors to be at the front, put them at the back

-100x100x3 is well enough for the base

-invert that motor on the Z so it's not so ugly sticking up, also all would look more compact

-This machine looks much like my first build combined with Deans Gantry design, so you can check how i made the z and maybe all the build log, furthermore i have the plans in sketchup for free

-invest in a proper straight edge and save on that epoxy, by just shimming the rails. Long ago when was making mine 1st build, i was insisting on the epoxy and wondering why Dean shims the rails, now i know, 200e in my pocket. i would buy calibrated steel bar say 40x6mm and epoxy that precisely to the frame and mount rails on top of ut

-check the Youtube video of that one i am talking about https://www.youtube.com/watch?v=C9hT...ature=youtu.be

-for a serious Z axis you would like to move the rails not the bearing carriages, furthermore overhang should be as minimal as possible and that a key in for a perfect finish on metal.

-servos are 10x upgrade over steppers IMO, go for it, 2:3 is the correct ratio for such machine, 400w 230VAC