I use a 'compromise' of 45 SC drops/ml in 'JuiceMeUp', regardless of the bottle size. That's why I stress keeping notes of any additions or lowering the drop count.
I start out at a low % and then up the recipe flav % until the JMU drops match what I actually use. Hope that makes sense...
Wouldn't adding drops also change PG/VG amounts as well as other factors, such as how much nic to use, or is all that negligible considering that these flavors are so concentrated?

