Weather was kind today so I started work on a prototype 'cavity base', which will have a slatted floor with a removable slatted-rack over it. The 'slatted floor' being an alternative to a mesh floor, as I have far more wood in the form of battens than I have metal mesh. This initial prototype will have rectangular battens presenting a flat upper surface, rather than triangles or tubes.
Being curious as to how much ventilation such a 'slatted floor' will provide, I ran the numbers: with 3mm gaps it'll provide the equivalent of a one square inch open hole, spread evenly across a floor 18 inches square. That, of course, assumes that the slots remain open and don't get clogged with debris from above. Only time and a 'bee test' will reveal that. Here's hoping ...
LJ