Teal can be quite a difficult feather to work with. Many "good" tiers have never really got to grips with it myself included. On occasion I have trouble.
Here is a wee Peter Ross variant of mine which I thought at one time to be "noo bad" but the wing lets it down as the barrings do not run into one another & are not symmetrical.
Buying good quality Teal is the best option & I believe that Cookshill will probably be able to help on that score. If you do not use good well marked Teal your are on a hiding to nothing to start with.
The little line drawing from my website shows a much better wing.
Tight Lines