Huge Tumble Turnover

I've been practicing front crawl for quite some time, however, I've never managed to do a proper Tumble Turn. Finally last Friday, I started practicing. The first attempts were horrible and included:

• water in the nose
• breathlessness
• giddiness.

In the course of the weekend, I made over 200 tumble turns. The movement is still far from perfect, but at least I got rid off the above problems. Nevertheless, I'm still not quite able to do the following in a swift and harmonic movement:

• Swim to the wall quickly
• Forward somersault when you see the "T" on the bottom of the pool
• Tuck your head in tight
• Put your feet on the wall approx. 0.5 m under the surface
• Stretch arms out before you push away from the wall
• After a brief gliding phase, start with either a flutter kick or a butterfly kick before surfacing no more than 15 m from the wall.

As you can see, there is no "T" on the bottom of the pool. But I don't think that's the problem...