Definitely only plan to be in the trees on powder days after the main runs are tracked out.
They call the Jaimie Lynn a directional twin and the year I have has 1/2" of set back.
Yeah I'd be tempted to try a more directional freeride board but still in your size. Last time I rode a 155 it just felt weird, no float and lower grip. It was also a twin which didn't help.
I ride with more like 1-1/5" setback, and a little taper helps too.