I did a test with strawberry (Lorann's, I think it was), and my notes called it 'a plastic-like taste, must be from artificial flavor'. I tried various combinations of flavor with: Ethyl Maltol (EM) solution, Citric Acid solution, 5% acetic acid solution (white vinegar), various Vanillas, Cream, Bavarian cream....my notes say there were over 500 combinations in all, and I only tried 12 of them at the time. What I labeled as 'good!' was equal parts strawberry, EM solution, and Citric Acid solution (these solutions were 1/4 teaspoon EM or citric acid powder disolved in 10ml PG). The EM gave a little sweetness, and smoothed out that 'plastic' taste, and the citric acid (I think wife got it at grocery store or candy-making shop) added a little tartness while bringing out more strawberry flavor. Once I had the ratios, I tried this 'doctored strawberry flavor' at 5%, 10%, 15%, 20%...until I got the strength I liked.
The ratio that I found good for me, which I liked at 15%. A sample given to a buddy (who still smokes 'ultra-lights' analogs) received a comment of 'a little weak'.