The reason for the 75ohm hard line is for the long run to my tower.
John, the mixing of 50/75/50 Ohm feeder will cause you all manner of problems as there is a transformer effect as per the link in my previous post. The effect will vary by band too.
For what it's worth, I am currently QRV on 6m with a 2 element quad that uses a length of 75 Ohm cable to transform 100 Ohms at the antenna feed point down to 50 Ohms for the run to the radio. You can't just mix feeders of different impedance without problems.