i was thinking of something like 'countersunk barrel nuts',
also known as "sex bolts" https://en.wikipedia.org/wiki/Sex_bolt
though i understand why having somewhat esoteric fasteners (or other essential materials) is kind of a no-no,
they'd look pretty sexy with your configuration if you ask me : )
do your bolts extend through the entire width of your case? or just stickout on the ends?
..//..
my understanding of the SD card is that it is really needed for certain functions,
like saving and archiving songs without a computer handy