I'm basing this on my own feet; I'm not young, I fall off high heels, and I'm not a dancer. I don't think you can have more than 60 degrees of bend on the foot and carry weight. The weight has to be on the ball of the foot, behind the toes, on transferred by the design of a shoe. Dancers, especially ballet, do a lot of damage to their feet while they exceed that limit. If you want that sort of extreme posing, don't forget the back of the heel. I'm not sure from the angle of the pictures above, but I think you'd need to pay attention to the line of the achilles tendon. And my final word on the subject is this. OUCH!!!