Black iron pipe is weak and I wold not use it for mast material, only 35,000 pound yield strength, more common steel tubing from a metal shop will push that to 75,000 pounds, and chrome moly steel is up around 120,000 pounds. Those numbers sound huge until you do the calculations and see how much force is applied to the unsupported section(above the top guy wires). I use 1026 steel which is the 75k for masts and have had it bend with just antennas on it. And that is 2" diameter .2 inch wall! Do the calculations please and make sure your install is safe!