You have to set yourself to throw a powerful punch, and Spinks would be on the move backwards for most of the fight. Foster was actually pretty good at protecting himself too; he was hurt plenty of times by heavyweights, but that was due to physicalities rather than a lack of skill. Foster was too weak at heavyweight, but Spinks is the perfect size at light heavyweight. Although it must be said I favour Spinks if he weighs over 200lbs.