Mamiya RB67 Pro / Pro S / Pro SD Back Cover

I started with @BerndPfeifer_2033527's excellent remix, however, the RB67 has an interlock that doesn't allow the back catches to be disengaged unless the dark slide is installed (which the cover obviously doesn't have). This cover just adds two pins to emulate the dark slide, allowing the cover to be removed easily and at any time. I also added some fillets and chamfers because chamfers are what separate us from the animals.

Unfortunately, this makes the back handed--it can only be installed in one orientation--unlike the remix this is based on, so choose accordingly.

v2 has some small improvements including making the pins more obvious from the back, so the cover is easier to orient, and adding the locating spline to prevent the back from sliding while installed.