Thanks for the input. To clarify, my merino tee is definitely 150 gsm. It is labelled as such and I was selective when I bought it. It weighs 5.4 oz. My coolmax polyester tee (which I bought in about 1998) weighs 3.6 oz, and the material is much thinner. In summer I rapidly overheat in the wool tee. I can't wear it when I go running, for example. It is light green in color, and the coolmax tee is a dark forest green.
I'd like to find something like the old coolmax tee I have, but with x-static fibers, or some other silver/quaternary ammonium treatment that controls odor. I don't expect any polyester to stink as little as wool after a couple of days, but I was hoping that advances in technology in the past fifteen years had produced something substantially better than the old-fashioned coolmax.
Thanks for the suggestions to look at the Railriders shirts. I think I'm looking for something more like an athletic tee, though (light knits worn by runners, etc.).