I noticed on small issue, that maybe you can think about correcting in future revisions ?
In addition to a C64 reset button via the serial port, there needs to be a second screw on the case. Putting the SD2IEC is no issue, however removing you need a bit of force. As there is only 1 screw on the left (tape side) of the housing and not on the right (the serial side) I felt I could not remove the unit without stressing it. The rear of the case moves, but the front of the case stays in the C64. You need to prise something long and thin between the C64 and the SD2IEC.