define fun in 8-12 kts and choose accordingly
ST137 W I had myself, nice not too wide, won't break that easy but more like 10++ kts (wide wood boards >= 80 cm suffer from contact with obstacles denser than air, like water etc.)
fun in 8-12 kts (planing) only with wide (especially wide tail) board and large sail
you on ST137 W and 8.5 and almost anybody else on iS133/W85 and e.g. 9.5 and anybody will smoke you, you might not even see anybody pass.