I haven’t used telescoping fiberglass, but I’m planning to build a PVC mast with schedule 80. 1/2" fits inside 1" fits inside 1 1/2" fits inside 2". Couplers and reduces to assemble it into a pole, guy wires and a base with sand bags to keep it vertical. Using two sets of 10’ sticks would give you 80’ height.

You could also look at the Buddipole which claims to work 40 m - 2 m with different coils.