[TowerTalk] Coax Question

[Steve London]

I am planning on taking two lengths of 75 ohm coax, running them parallel to 
each other, and connecting the shields together, to create a 150 ohm parallel 
line from the two center conductors.

Is there any reason to think that the velocity factor would be different than 
that of the 75 ohm coax ?

Thanks and 73,
Steve, N2IC