Yes, I did have a look at your shot Ribby and it will sharpen, but you've got the optimum point of focus midway between the far and near edges of the nut - not necessarily a bad thing, but a smaller aperture might have got both edges in focus. I say 'might have' because as you've discovered, DOF is severely limited at macro distances even with smaller apertures, and significantly smaller apertures usually means using a tripod... or flash, but that's macro photography - very demanding but very rewarding when you get it right.
Excellent shot with nice subdued colour.
