Problem with the stretch cut

[Strikerche]

When I do the stretch cut I have this problem : If I try to bring the top pack to the bottom, it works perfectly. But the moment I try to cut the bottom to the top with my thumb I fail miserably. Can someone explain to me why is this happening, does someone have the same problem and how do I fix it ?

 

[Alex Hancock]

This is a rubbish answer I know, but practice. I found the basic stretch cut really hard - then with practice I could do it. Its the same with the bottom one. It's just more of a stretch.