Dry AND extra dry vermouth martini- what’s the right ratio?

I recently had a martini that changed my life at a restaurant in Atlanta. It included both dry and extra dry vermouth, and gin.

I don’t know what ratio they used and I can’t find many recipes that include both vermouths.

Has anyone made something like this? I’ve played around with ratios and haven’t landed on one I think is excellent.

(I’m using St. George Terroir gin because I love it. It is not the gin the restaurant used.)

Anybody have a good recipe for this?