Looks to me like pins 1 and 3 and 4 and 5 would need to be small coax like you said (RG174 for example) even if the connecting length is only 2 ft. or so.
I looked at the cable on ebay. Very nice, good price, but seller doesnt say if all the pins are connected. It is unlikely that any are coax or shielded.
Thanks for the info.