New filament spools from a different supplier were wider and could not fit in my original/ old design (http://www.thingiverse.com/thing:773044) so I made version 2, here, that would fit multiple reels in a single box.
Added a simplified filament dispenser opening that prints a lot faster. But requires a pair of M3*8mm screws to secure, and a short PTFE tube to provide a smooth flow.
The spools are held by a 1.5 inch PVC tuning, mounted on both sides of the box with M3*8mm screws. Spool separators prevent/ minimise spool contact (inspired by a design I saw on Thinginverse, but cannot recall where).
Suggestion: Mount spools in opposite directions, mount PTFE holders in alternate top/down configuration to prevent spool entanglement. Works for me.
Hygrometer mount can be found at my original design (http://www.thingiverse.com/thing:773044)