How can I accurately get the surface resistivity of these irregular samples?

i.sstatic.net/7HLvVJeK.jpg

I'm not sure whether I should use the 4-point probe or van der Pauw method on these samples to get the surface resistivity of the curved face. The dimensions are roughly 12.7 x 10.7 x 1.7 mm, but the bulge peaks the height to 2.4 mm along the center axis. I've tried looking at correction factor tables but none of them include a similar shape, the closest one I found was a rectangular block for the 4-point.

How do I pick between the methods, and what setup should I use? Also, what kind of accuracy can I expect?