Fear Uncertaintity Doubt
It discourages learning and kills countless projects every day.
I see it on all the ham reflectors.
Well casing is a known material with known characteristics.
Buy it in unused condition or have it surveyed as drilling tends
to thin the walls.
It's cheap in Tulsa, Galveston, Houston, Lake of the Pines,
Tulsa, Lafayette, etc. The math is not difficult and any
introductory statics book contains enough information to
design a safe structure. Has what you need to design your
concrete base 'structure' for an 'unguyed' as well. One might
also pick up an introductory soil mechanics book for base
size and shape design.