Flush setting in a dome surface???

[HeatherMarie]

Hi All,
I'm working on an order, where I'll flush set a 3mm faceted blue zircon in a sterling silver bar necklace.
I will solder two layers of 18g sheet (approx. 1mm each layer) together (to add more depth for the stone), then will flush set the stone in the center of the top layer.
My concern is my two layers together measure approx. 2.03mm. However, the depth of the two stones I have to set is ~ 2.05 and ~2.06mm (my backup stone in case one breaks in the process is 2.12mm). The math just doesn't add up-- If the silver surface is measuring 2.03, but the depth of the stone measures 2.06, will the very tip of the cutlet be slightly sticking out of the backplate?
Once I solder them together, will that add enough more depth to make it work?

Having this concern, I thought I might dome the top layer, so as to add more depth. However, I've never tried to flush set a stone inside a domed surface. Is this possible? Will I run into any problems soldering a dome on top a flat surface, then drilling my hole through it (pressure inside?). Will there be enough surface area for the dome to successfully solder to the flat backplate?

Any other creative solutions or ideas?
Please advise! Check out the pics I've attached for reference. Thanks so much!

-Heather