I haven't used any of those flavors, but I would think your percent of Mango could be lowered to the half. If it turns out a little harsh, add a sweeter flavor or a sweetener. I'm sure some of the experts will chime in with a better answer.
Personally I don't find I need to add more flavor if I change the ratios, but I know many others do. As long as you're at 30/70 I don't really think you'll see at whole lot of difference; if you're going max vg you might want to try it though, because pg is a better flvor carrier than vg. I have also vaped a lot of 0 mg nic mixes and have never changed anything in the recipes, if anything it gives you a more 'clear' taste imo.
And don't listen to Tiny up there @AZViking
I knew this would come in handy