Since you need to hug your partner's head, you need to utilize a low mount. Note that this is the same position where you might set up an arm triangle or reverse armbar. I personally prefer to cross my feet any time I have low mount, but it's up to you whether you use grapevine hooks or crossed feet; the really important measure is whether you can get your hips low enough to catch the neck with your arms. Once there, you may need to do some "swimming" (arm pummeling) to get back to the inside (and, ultimately, to your partner's neck). Finally, a three-finger grip might work better for you than all four, particularly with the index finger getting in the way.