As I understand it...
Provided the mounting points can take the strain, your constraints will be that the pads are fully within the area of the disc and not overhanging (this can lead to the pads touching each other when worn in and not braking the disc), the caliper body or retaining pins are not rubbing the rim of the disc and that you can bleed the caliper somehow with the bleed nipple at the highest point.
I got around the bleeding bit by bleeding the caliper off the CK on a spare disc (it is mounted on flexible hose) and then underslinging mine. Not the easiest thing to bleed but do able with a bit of patience and time.
Hope this helps