Hi! Are you just making that for yourself or would you be planning to sell it to others? (Asking, since Easyrig already TM’ed it, hence I’d only make it for myself.) Obviously, it would have to be something you could move a bit left and right. The cheap pipe clamp would do the job. Bolt looks nicer, but to make it adjustable, you’d have to compromise the stability of the crossbar. Or forget about left/right and just go with a single hole. Would be the most aesthetic option. 3D print might work, but you’ll most likely have more of a problem explaining a possible damage to the camera to the insurance company, when that print breaks. A situation I wouldn’t put myself into.