North-south turning drill

This is a drill I made up a few hours ago.
It's primary goal is to build up strong turns.
A side-effect proved to be that the one holding get some grip training.
In the pictures I'm not warmed up, used to the drill or anything. Due to this we used a grip that made it pretty easy for me to turn around. Having the Gi on makes it easier for the grip-holder to keep the grip even though I'm twisting myself. First time you do this drill start with the grip shown in the pictures and then get firmer and firmer grips.
Maybe something like this.
Grip 1. Firm grips with outstretched arms on each shoulder. (As shown in pictures)
Grip 2. Grab the arms.
Grip 3. Pin arms and elbows to the ground.
Grip 4. Plant forearms on shoulders. Grip with hands on something like.. lapels, belt or extra skin on stomach (if no-gi)
Grip 5. Full north-south position.
Gripd 6. North-south position with lapels stretched under armpits.
And so on.

• Start Position

Start position. My dad Sören is holding my shoulders down preventing me from twisting my shoulders and turning myself around.
• Shrimping

I begin to shrimp. In theese pictures I cheat a little by going outside his right arm with my head. It worked that way but wont work later on if firmer grips are applied. The grip-holder should now work straight down and put all weight on my shoulders.
• Still shrimping

Important note is the the holder should continue to work against the twist all the time.
• The turn

Bring the leg closest to the ground/floor/mat/tatami under the other leg and turn yourself. When doing this the elbow of the holder gets contact with the back. This will give him great power and will probably completely block me from turning more. When I come to this stage I stop the twist and return to start position.
• Start position again

Back to the roots.
• Other side shrimping

Here you see what I do with my head. Going on the outside with my head makes it easier to shimp and turn. But in actual situations this probably wouldn't work.
• The last turn

Same as the other side.
After this you go back to the other side and repeat.
Try different grips out.