In the final analysis, the capabilities of a boat (bluewater, coastal, inland, etc) are determined by the master (& crew) - and second guessed by everyone else.
“A” (Unlimited Ocean) STIX Value >32 - adequate to withstand up to a force 10 gale, with average waves of 7 m height and eventual wave heights of 14 m.
“B” (Offshore) STIX Value >23 - adequate to withstand up to force 8 winds, with average waves of 4 m.
“C” (Coastal) STIX Value >14 - adequate to withstand up to force 6 winds , with average waves of 2 m.
“D” (Local) STIX Value >5 - adequate to withstand up to force 4 winds, with waves of 0.5 m maximum.