Last year, i went to visit Oliver Rolf from Platinum, and he showed me an image, that i would guess its around 30x40" made from a half-frame negative. I loved it, and of course it was taken with an Olympus Pen. He would make a point that as long as the camera and lens is good enough, it will not matter. I cannot say this for sure, but i would even believe it was made with Tri-X, he has an affinity for that film. Not without reason of course. Not to mention that because of the distance you will need to properly view these images, you will not notice anything at all.

(and if you do your math, 30x40 is half 40x60, so thats the exact same "resolution" you will be getting from a full-frame neg enlarged to 40x60)