"i am" i posted this thread to get a different perspective.
personally i would move my hips back and pummel for position. no strike would have an effect at this point so you have to counter the clinch first.
the only other option that is practical that i know of would be a throw, which is often seen in judo in this position.
if you want to my know experience ive been in this position sure, ive dealt with college wrestlers and such coming in at a solid 280+ pounds, but my background in grappling isnt wrestling so i use other methods like the muay thai clinch for controll or i will use a leg lock or wrist and head like a wrestler, i havent used underhooks offensively because i dont feel comfortable embracing someone when what i really want to do is put an elbow in their face. so i use the methods above when grappling lol for better or worse haha