Armed with this knowledge, I mixed them all up together, fiddled with the proportions a little - and it was good.
The French Bulldog
1.25 oz gin
1 oz Texas Rio Star red grapefruit juice (these are back in season - so love your booze and make it fresh.)
1 oz St. Germain Elderflower Liqueur
1.25 oz Dry Lemongrass Soda
1.25 oz Dry Lemongrass Soda
Combine the ingredients in a mixing glass (a pint glass works well) full of ice. Stir for 30 seconds and strain into a cocktail glass.
Verdict: This drinks wins for both ease of creation and sheer deliciouness. It's a beautiful balance of all the flavors. And it doesn't hurt that it so damn pretty.
Edited to add: It looks like the jerks at the Dry Soda Company have discontinued the lemongrass flavor, so if you must have lemongrass soda, you'll have to make your own. Or, what is much easier: substitute lemon perrier for the soda. I promise it's just as delicious.