I'm with RS, just for the record...16 gauge tubing has a wall thickness of about 1/16". That's pretty thin stuff, but as you know going to 1-1/2" schedule 40 galvanized pipe (1.9" OD) doubles your price (at least), but gets you over an 1/8" of wall thickness. You might be able to save some money by going with the 1-1/4" schedule 40 pipe...1.66 OD with 0.14" wall thickness compared to the 1-1/2. I would prefer this over any 16 gauge materials for general strength, abuse resistance, and long life/ rust though resistance.
Don't get me wrong, the 16 gauge will likely work, but stepping up to schedule 40 will work much better and last a lot longer. I can see having problems driving the 16 gauge pipe into the ground with a post driver...mushrooming the tops and maybe even bending the pipe near the midsection. I have not done this as I floated my dock on the Playstar floats. Let us know how it goes either way and be careful driving those posts while on the ice.
