I'm doing 132x40 with channels and concave, on the same rocker, with ~10.5mm core, still in cedar.
Glass will be 6 oz plus local reinforcements.
I think I can get away with this because I want more flex, and the core shaping will hopefully keep it from being too much.
The X factor is that the new core is a single layer without epoxy in the middle, so it will behave differently.
We'll see, it's more alchemy than science
If I were using redwood, I might go thinner, especially from the straps outwards, and with maybe a maximum 8 to 10mm between straps, probably with more glass (6oz+4oz? 6+6?), since redwood can be more brittle than cedar. ? I don't know...