Hey you!
Thanks for the heads up on your hand positions… 
The thing that comes to mind is a very common mistake. Perhaps you have your feet too far apart. I have a blog posting on this and it has photos as well. You may have seen it and thought it wasn’t for you because of the title, but believe me, this is THE key to this pose. Here is the link:
Opening up your hamstrings with hot yoga
Ideally you want your fingers to come in from behind the heels at an angle. You will probably find it a heap easier when the feet are only 3 feet apart. The ‘dialog’ says 4 feet. This causes a number of problems especially if you are very tight or shorter than average;
including back strain and grip problems. This pose is about the stretch through the whole back of the body. It should feel delicious. I hope you can tweak this with me, because I am sure with a little toing and froing you can find the sweet spot for you.
Over to you s_i and please get back to me soon…
Namaste
Gabrielle 
PS I do have other ideas for you in my ‘toolbox’ but let’s please knock off one idea at a time here!