I think Bonnar destroys Kos if they fought in open weightclass, Bonnar is 6 ft 4 in (1.93 m) & Kos is
5 ft 10 in (1.78 m). That's a HUGE size difference & Kos would be f*cked. But if they somehow meet at MW then it's a different story, I don't even see how Bonnar would make that weight and if he did he would be messed up, while Kos would be around his normal weight & probably would fight even better than he does at WW. I don't see this ever happening tho.