Read the training article again.
Keep flying the young birds.
A training bird only makes things easier but is not necessary.
The performance has been engraved into this breed.
They will do what they can do sooner or later.
As long as you keep the discipline in mind at all steps.
It is not necessary to pull any feathers for any reason.
It is only suggested for extreme cases of birds who are unable to fly from tumbling and everything else have been tried.
I am not sure what you mean by half takla.
Grab your cell phone and shoot a video of what you are talking about.
Maybe it will be helpful.
Are you talking about riding the tail?
I am assuming you are getting frustrated because the birds are not performing after 10 weeks??
If so it is no justice to them.
It is still early and reading your previous message on how you are keeping them it is most likely not entirely (or at all) their fault.