I never liked Leonard at 160 pounds, Minter is a VERY live underdog and if the odds looked good I'd bet on Alan.
Neither Sibson or Longer are close to the class of a Leonard. The 1987 version of Hagler beats both of them and rather easily. Sibbo got dropped and stopped by DON LEE so give me a break. Minter and Sibson were nothing more then soild pros. And I would argue had they fought in the era of Eubank/Benn they would have come up short as well.
Before getting stopped by Tony Sibson in an upset (it was to me) Minter had always displayed a solid chin. In his brief fight with MMH the Marvellous one admitted Minter could bang too. Leonard wouldn't stop Minter unless he cut him which you couldn't count out. Minter could also box when he felt like it. I'd still favour Leonard over the distance though