Matt Hughes in today’s WW division would be small compared to guys like Shavkat, Garry, Usman, JDM, Edwards. He would fight at LW today, Matt walked alright 175/180 lbs. Sherk would also be a FW today, in today’s LW division he would be a smaller LW, Sherk was 170 off camp. Gomi was by no means a good size LW Lol, he was 160 off camp and barely even cut weight, he like the others would be a FW. So all of these guys would fight in lower classes.
GSP had a close fight with Penn in the first fight, but Penn got dominated in the rematch. Keep one thing in mind here, GSP put on size as his career went on. GSP in 06 was about 178 and in 09 was 185-190. He put in size to compensate for the bigger WWs and his grappling heavy style and a potential move to MW. And you can see in the rematch how much more dominant GSP was, he was bigger. Fitch was a bigger guy no doubt, I’ll give you that. But Rory and Nick he heavily struggled with.
So the points stand. Penn was able to do well vs these guys as they are comparable in size. And these would mostly all be in lower classes today. So it’s not like Penn would go up to WW or MW today in his prime and have any success, he would get killed.