I find I get into that position when they are trying to dig their knees in to split my guard. If I can reach their arms, I'll normally try to brake down their "stiff arms" and clinch them again. If I can't break their grip in time, I'll lift my hips up onto their thighs to release the pressure.
From there, like mentioned above, it depends what they're doing.
Weight backwards, sit up into their lap and work hip bump/what ever works from there. He'll normally try to drive you back to the mat. Return to controlling posture.
If they are postured up, and you can wrap up their head, don't forget to drive your legs down into their hips to stretch them out (like the main way Eddie breaks posture)
Also, don't forget to pull them into you with your legs. This can fuck up their game if they can't get set.
If you can bring their weight forward, so they aren't sitting on their heels, you can shove your feet between theirs, grapevine their ankles and stretch them out, giving you enough space to stick one or two butterfly hooks in, and play from there.
You can always uncross your legs and play open......... (jokes)
Don't know if this will be of any help to you.