There is only a .3 DB of loss difference between the regular and flex LMR400 in your 50 foot run. Nothing to worry about. I would just go with the LMR-400-UltraFlex. Here is a link to the Times microwave coaxial cable calculator... http://www.timesmicrowave.com/calculator/?productId=52&frequency=435&runLength=50&mode=calculate 73 Jeff kb2m