Snatch posistion - active stretches??

[strengthsupplies.com]

I'm gradually getting better in the bottom snatch position, but i still need some more flexibility to stop my shoulders rolling up and forward at the bottom.

After reading the book i think i need to work more on an active flexibility to hold the position.

Does anyone have some ideas on what active stretches would be good to help maintain the shoulder position during the snatch/snatch squat?

Or even just a bodyweight squat with arms pointing straight to the sky? Mine tend to pull forward a bit before half squat.

[Thomas Kurz]

For exercises to strengthen scapular retractors and increase shoulder ROM see Strength and Conditioning Journal vol. 27, no. 4, pp. 36-45, and vol. 28, no. 3, pp. 62-65.