My first mast had 22 mm core with 1 layer 6oz +-45° carbón 2x2 twill(0,25MM) and a
2 oz fiberglass layer.
No problem on longitudinal flex but more torsional flex.
Maybe this is better
2 layer 6oz +-45° carbón plain weave(0,5MM)
2 layer 15 oz triaxial carbón 12k 0/60/60(2mm)
1 layer of 15 ozz Fiberglass +-45° (1mm)
1 layer of 15 oz Fiberglass +-45° (1mm)
10 mm bamboo core
1 layer of 15 ozz Fiberglass +-45° (1mm)
1 layer of 15 oz Fiberglass +-45° (1mm)
2 layer 15 oz triaxial carbón 12k 0/60/60(2mm)
2 layer 6oz +-45° carbón plain weave(0,5 MM)
Somewhere in 18mm to 19mm range.
More carbón on the outside