Since I have the 6-footers coming I'll give those a shot and switch if we run into problems (which I don't anticipate).
Previously to getting the directional antennas, we had the stock whips from Sennheiser mounted to the front of our sound rack BOH (approximately 70-80 ft. from stage) with occasional issues. I think, even at 80% efficiency with the directionals, we should be sitting pretty.