Jtek Clamp-On Double Frame Cable Stop - Silver

Hi, I am looking for some downtube cable stoppers for a 90"s alloy Principia frame, the circumference of the downtube is about 12 cm Which clamp diameter should I order, we dont think we can use one of these 'IRD Quick Release Down Tube Cable Stop Adjusters', that are available on this site, cause in the frame there are just two holes, and we dont see how we could install them The original cable stops were not deliverd with the frame, kind regards So my only hope are these clamps