By the way, I do structural engineering for my day job, and I took a look at the 10165P AntennaCraft 16-gauge 5' pipe. I couldn't find any specifications on the type of steel that is used to make it, but I would assume 36 ksi steel. It could be a little lower, but I wouldn't think by much lower than that. This is a good low guess, but I'm not 100% certain. The outside pipe diameter is 1.25" and thickness is 0.054". It's also galvanized.
If you mounted an antenna at the very top of the pole, and the bottom was attached to a rotor (or other support), the maximum allowable load that could be applied at the top of the pole would be only about 34 lbs. horizontally (MAXIMUM) before the pipe yields in bending near the bottom. Now if you mounted an antenna at a lower elevation on the pole, that would greatly increase the allowable load that could be applied to the pole. At 3' above the rotor, the maximum horizontal load would be 58 lbs. that the pole could handle. At 1' above the rotor, the pole could handle a load of 174 lbs. But that is the absolute limit, which you don't want to come near.
Keep in mind, the antenna rotors have their limits too. The Radio Shack rotors have the maximum antenna heights listed in the user manual.