It varies pretty widely @welshman68 . I’ve never mixed anything above probably 6% and usually much lower than that but I do only seem to buy strong concentrates (FA, inawera, atmos labs etc.). I think the weaker ones it’s usually one shots and suchlike, which I wonder if they add pg to the concentrate to make it easier for the user to mix and calculate percentages?
I had a look on elr and people are mixing this one at 2%. It doesn’t get very good reviews though, there’s only a few and they seem to be saying that the menthol masks any tobacco flavour that’s in there. But I’d start at 2% and see how you get on, taste is very subjective, you know?