Here we use...
1-1/4 for 18 inches above the roof
1-1/2 for 2 feet
2" for 3 feet above the roof and/or a pull of 30 meters.
then there is the 8x8x20 foot posts we bolt onto the side of a building and run a pvc up.
Edit: We don't fool with a mast. She is bolted with two 1/2 bolts to the structure. One near the meter base and one near the eave, always at least 18 inches apart. Mast bolts we call them.