Nana bakes concentrates

[Jugg1es]

Ok, Christmas day or boxing day I will get to do my first mixes. My first is going to be a custard (capella) followed by a fruit for something to take to work.
I recently got 6 part bottles of nana bakes concentrates in a giveaway here and can't seem to find much on them for vaping, I know they are pretty concentrated and would appreciate some advice on them.
1. Safe to use?
If 1 is yes then....
2. What sort of percentages should I use (banana custard springs to mind)

 

[Chegs]

TBH,I found the NB concentrates variable in use.A bottle of Aniseed is really strong at 2-3%,a bottle of Banana was so weak I used the 28 ml concentrate up in about 4-5 bottles of juice,using 20+ % concentrate still produced tasteless juices.Strawberry was another weak concentrate,I'd give you a fuller list of the stronger concentrates if I still had any (used up making lots of tasty juices a long time since)