I have been working on the development of the modular/permanent layout. Here's the latest iteration. The modules are pretty easy to see. Along the walls there is a two level shelf layout. The module rail height is 48". The two shelves are at 45" and 59" respectively. Access to the upper level is via the helix in the utility room at the upper right.
The interior of the loop will only be accessible via the wye when ops sessions are conducted and there will be no ability to go completely around the inside loop. The fiddle yard will be at the end of the lower shelf level and inside a closet below a set of stairs.