I only have the one infinite light as BB mentions above, 1600% intensity, 10% size, .5 shadow blur radius. I figured out how to make the caustics show up, by resetting my shadow blur radius to 0. Too sharp on that, but if I bring it up past .005 it's too fuzzy to see at all. Not sure why. I am using your volume box and gobo as loaded straight from my prop library. It can't be a scale difference thing, I'm using poser native units as well.