Well thanks for the support!! I really appreciate all of your comments!
For those interrested, here's how you do a decapitation:
You start the same until stage 4.
Here how it goes after
[...]
4. Hold both pecs
[space 3x]
5. Hold abs
[space 1x]
6. RAISE shoulders
7. Extend abs
8. Extend hips
[space 4x]
9. Contract both glutes
10. Contract knees
[Press P or do whatever you feel like]
Et voilÃ*! Clean decap! Worth almost 60k of damage.