Hi Austin...well, i'm thinking of plate steel a few mm's thick.......like a shelf...cut to the same shape and dimensions as the side of the CX 100.....
Then go to the back of the shelf...and weld an upright there...that would act extend up to the back of both speakers when on their side and stacked...
The upright would have holes drilled to match the stock mounting holes of the CX100's...
THen run a bolt through the upright and put a "butterfly" opening nut on that and "pop" that into the back of the stock mounting holes...then you can tighten up the speakers to the upright...and kinda lock it all togther...