Help with HP 4951B protocol analyzer + 18179A

I'd read that too, but somebody sent me a private e-mail saying that the mating diameters of the inner pins of both types of connector were the same, it was the outer diameter of the socket contact that differerd (so as to give the right characteristic impedance with the dielectric used). And therefore there's no mechancial problem in inter-mating the wrong connectors. And for this application there's no electrical problem either (the other end of the cable has an RCA phono plug on it, well known for not having a defined characteristic impedance). Any mismatch at the BNC end would cause no problems. I feel like getting a couple of plugs, one of each type, and sticking a micrometer on the centre pin. And I am not going to trust the no-name ones from the local hobbyist shop either (who knows what spec they're made to!). Then I'll know (hopefully) for sure. -tony