My remote SD mount consists of three pieces.
GDEMU SD Mount 1.2.stl
GDEMU SD Mount Bracket 1.2.stl
GDEMU SD Mount Button 1.2.stl
In addition to the printed parts you will need some additional parts.
The 15cm one will be more than long enough
M2x8mm (You will need 2 to secure the SD card extension to the mount.)
M3x8mm (You will need 6 of these to assemble the parts)
M3x16mm (you only need one for the front most screw hole)
Everything should print without supports.
Assembly is simple, uses two M3x8mm thread forming screws to attach the GDEMU board to the SD mount bracket.
Screw the SD extension into the SD Mount.
Plug the SD Extension into the GDEMU.
Place the Button into the SD mount, and attach the bracket to the SD mount. Use 4 M3x8mm screws to attach the parts together,\
Install the GDEMU just like the original drive, use an original drive screw to attach the back mounting hole, and use one of the M3x16mm screws to attach the front screw through the GDEMU board into the Dreamcast.
Thank you to Marcus9199 and bpv6ja for testing the design and providing images of their finished products.
I have complete kits of this mount available on my website