focus - How can I get perfect sharpness when shooting still art?

I've been trying to shoot some marble sculpture that are well lit on a studio wall. The photos are coming out well and perfectly useable.. but I'm striving for something better. My issue is with sharpness, I can't get everything perfectly sharp. Any tips on top of what I am doing:

1. I'm using a tripod


2. Canon 5d mark II with 24-105 as well as nifty fifty


3. Aperture highest the lens offers


4. ISO 400 or lower


5. Image stabilisers off


6. Long and short exposures 4 seconds - 1/500


7. Focusing manually using liveCode zoomed in 10x



8. 1.5 meters from the subject

I'm getting great shots.. but I want to capture all the fine details of the stone, the textures and veining etc.

I can sharpen and boost the contrast etc in post and get some pretty nice images.. but with the source images being a little off, you can never capture that perfect photo.

http://www.thisiscolossal.com/2014/03/airy-dresses-carved-from-marble-by-alasdair-thomson/