Re: irimi nage spinning
(shoot, I told myself I wouldn't post in these threads) I like Pauliina's and Daren's posts. To add a physical reference point, if Uke's head is not between your shoulders you probably have given them back too much balance/ let them too far outside your center.
This may sound stupid not knowing what style you practice or why...but
1) Take a look at Gozo Shioda's basic form of shomen uchi Irimi-nage ni in any of his texts. Break the waza down into that simple form...maintaining your posture, breaking uke's posture. Use movements of irimi (shuffle enter), tenkan (pivot without letting uke's head go past your back shoulder), body change (turn on the balls of the feet, from weight on knee closest to uke to weight on the other kneee), body change back with atemi.
2) Then look at many of the "flowing styles" of aikido and how they do it. Then try to take 1) and begin merging it with 2) and see what you discover. Its a fun ride...