Everything goes together pretty tight with the current design, but in a good way since there is just enough clearance built in to allow that. I was concerned due to the number of parts that it would feel like a solid piece but that looks like it won't be a problem. The parts actually inter connect a bit which helps with that. The base which holds the breadboards includes some round bumps which lock into the holes on the Stanley organizer. That feature should help keep it all in place when it is being transported. I still need to work out a few odds and ends but the design is around 95% done.
You can find the final version of breadboard kit and parts at the links below:
DSO112A Module for the Modular Breadboard Kit :
https://www.thingiverse.com/thing:3638866
Component Tester Module (blue module show in the pics below)
https://www.instructables.com/id/Component-Tester-Module-for-the-Breadboard-Kit-V2/
Small Modules here:
https://www.thingiverse.com/thing:3416074