The modern Copal and Compur shutters will work in any position. The main "issue" is clearance for the cable release in relation to the construction of the front standard of the camera. As an example, copal 3 shutters have the fitting for the cable release sticking straight out, not at an angle like the Copal 1 shutters. Thus it is possible that the cable release may be blocked by the posts that hold the front standard unless you angle the shutter up or down a bit. Older "pneumatic" shutters, the ones that have air pistons that descend by the pull of gravity need to be orientated with the top of the pistons up.