Toshiba Canvio Basics 2.5" External HDD Under-counter Modules - Expandable

I searched and searched for a 2.5" external multiple module HDD under-counter mount, but alas couldn't find anything suitable...so I created my own.

I'm still learning 3D design using Sketchup, so this was a bit of a challenge at first, however the design, fitting and sizing turned out perfect!

Brief:
I wanted to be able to mount 3 of my external Toshiba Canvio Basics 2.5" HDDs under a shelf above my PC box, but they also needed to:
- have a universal backplate to stop the drives from sl