Didn't zone out, I always listen to Kevin's shows. Missed this one live, and planned on listening to the replay even before I saw this thread.
I have one of those cheap plastic battery cases that holds two 18650s. I'm guessing the Eclipse.....( oooops...your mod....) will be a little bigger than that. That's actually a nice size if that's the case. Fits in a shirt pocket, fits well in the hand. Probably just a little taller and thicker than the typical homemade box mod.
The casing is 100% custom designed. It will be as compact as possible to house everything.
If you are comfortable with the size of what you have, I think you will be pleasantly surprised.