@ iver,

I see what you mean. So basically i need to change by base leg so im lower to the ground and so im not arching my back so much. Ill look into it when i get home tonight.
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so i find that the o guruma is not like the powerful 'goshi' throws. in throws like o goshi and harai goshi youre throwing your opponent over your hip which is why as you said, you need to face the ground and stay bent foward because youre carrying your opponents weight on your hips and back.

o guruma is different because youre rotating your opponent over your leg as it were a physical axis. so yes its not good im arching in the demo but it allows me to sneak my 'axis' leg around uke. when my base knee extends it gives enough pop to set my back straight and lift uke's weight and then the rotation begins.