Commodore 1541 FD Case

This is a WIP that I need help with. I used Sketch-up and export to STL. The result is poor with the STL model needing fixing. This is where I need assistance. Can someone look at the model and fix it? All that I have done results in missing walls etc.

It is designed and scaled for the C64 mini as a USB hub case. I posted an prototype build on the "Thec64community" that used an off the shelf electrical box but felt it fell short of my vision.