Headstand form

Any tips? I've been stuck like this for a while. I'm trying to learn a free-hand headstand. Any headbalancers out there? Just out of curiosity, is handstand form similar to headstand form?

Thanks so much! 

 

http://youtu.be/ikaybl3C1AU

 

https://www.gymnasticbodies.com/forum/topic/3501-head-stands/

Bonus advice not in that thread: Gym floors function somewhat like donuts, since they dent in. I can head balance much better on gym floors than on flat surfaces, but am able to do either fairly well. :-)

straighten your legs, point your toes, don't pike, and be slightly hollow