How many midi channels on one midi 5-pin cable is reliable?

Just so you know, you can enable sending MIDI clock in Cubase on a per port basis (as it is global), CTL+Click on the transport to access the settings. For example, a couple of my MoogerFoogers will synch to tempo via MIDI port, but have to have the clock. Or, my Voyager can sync its LFO to MIDI clock.