I have tried :
1DX, 100L, combined with kenko 12 and 20 and 36 and 2XIII.
The only way that I could work with this combo was on a tripod and using Helicon software for the focussing and image stacking.
Focussing by hand is next to impossible with such a limited DOF.
I will post some images later, comparing the 100L as is and with the combo.
Hope this helps
And the pics. The shell is approximately 8*3 mm in size