Yes. Too much. Leonard wasn't a great super-middle, and was very beatable at that weight, at that point in his career. Froch had trouble with speed and movement, but the size and strength difference is too much in this one.
I think Froch would be way too much. Size, strength, power and while speed bothered him Leonard doesn't have the physical aspects of an Andre Dirrell nor the spoiling aspect. Dirrell was really really fast for his size and had good pop. Leonard was no SMW and had to be a crazy weight bully/promoter to even get Lalonde in his sights. Leonard opens up a lot more than Dirrell and would give Froch a lot of opportunities to get shots off. Froch also fought some slick-ish fighters like Bute, Taylor, and Groves and was able to crush them all because they all opened up, which I think Leonard would do.
It's a curious one with Leonard. Despite being the first guy to win titles in five different weight classes <insert footnotes and annotations>, he was clearly at his best at his primary weight class, and he doesn't travel too well outside of it in H2H match-ups. I would only rank SRR above him at 147, but I don't think he was that great a middleweight, never mind anything higher.
adage; a good Big Man "what's" a good small man. Strength & Height, reach, toughness & durability over the great Boxer. too much to give away here, as it usually always is in these cases, usually!
Just for the record, Thomas Hearns was the first ever five weight champion. Hearns made history by beating Kinchen on 4th November 88. Leonard became the second five weight champ when he beat Lalonde on 7th November 88; which was just 3 days after Hearns did it. It was close, but Tommy got there first.
Working from memory, and it’s not an exact science, but was the win over Kinchen properly recognised as a title win at the time? My recollection was that the WBO didn’t really gain “legitimacy” for a while after. Legitimacy is obviously an oxymoron for the alphabet brigade, and you can’t really split hairs for Hearns bearing in mind how Leonard won his 4th and 5th titles. I don’t mind either way. Hearns was clearly better at moving through the divisions though, which makes sense with his frame. Hearns was a very good LHW, and still possibly the best LMW of all time.
It’s true that the WBO was lightly regarded at the time, particularly in the USA and Hearns Kinchen was the first ever WBO title fight. If I remember, the US commentators considered the NABF title, also up for grabs, as more prominent. Nonetheless I think Hearns did get the credit as first ever five weight champ immediately after the fight. I believe Hearns was initially scheduled to fight for the WBA super middle belt against someone else, but it fell through and the newly created WBO jumped in with a better offer. Leonard’s fifth title was probably more controversial. Leonard and Lalonde fought for both the WBC super middle and WBC light heavy titles at super middleweight. Lalonde had to boil down to 168 and his light heavyweight title should not have been on the line. What’s more, Leonard struggled to make the super middle lower limit and later admitted to having weights in his pockets at the weigh in. Leonard was allowed to win a light heavyweight belt without ever boxing at the weight. Unbelievable, really. Lol. Only in boxing.