2020 & 2040 X Y Z carriage

These are some carriages I designed for my DIY printer, they still need some work when the aluminum which I ordered will arive.
They are "addon" parts for my 2020/2040 slider (https://www.thingiverse.com/thing:2395921) I designed.

This thing is designed to use M3 cap hex head screws and a M8 Longnut for the Z-slide
Screws fitting: M3x12 Hex Cap Screws


Please share your ideas and thoughts about this with me!

Update:
12.07.17 - removed unneeded hole from the carriage and added a vers