From 30pg/70vg to 50pg/50vg. I don’t really calculate it much, I just see how it goes. The aroma ratio also varies depending on recommendations and taste. 
Solomon isn’t for me, but for someone else who has been hopelessly looking for something like this for a while. 
Are you interested in a dual or single coil RTA? With what diameter?
I can mostly speak about dual setups.