AA to C Battery Adapters/Spacers

Yet more AA to C battery size adapters.

I considered enif's excellent AA-to-C adapter design here, https://www.thingiverse.com/thing:1719966 , but in my version the flexibility is determined by slicer parameters (more perimeter layers and higher infill density increase rigidity, and vice versa).

I've also included: * a gapless version (which is fine when there is no need to stretch to accommodate a larger-than-usual diameter AA battery). * a side-insert version (in some devices it's easier to first install the adapter and afterwards install the AA battery from the side, but with this version the battery could fall out of place if bumped since not held in place from all directions).

My SCAD file is also attached for your customizing pleasure.