well fighters in most sci-fi series including B5 are used for taking out the engines/weapons of capital ships. so the weapons are powerful enough to do this even on fighter sized craft. so capital ships should have no problem causing the crits on each other no matter the size.
bigger ships can just survive the hits longer and effect repairs.
it should be no harder to ever cause the actual crits, bigger ships just tend to have more back up systems and so can generally ignore the effects of the crits.
also under this save thing as you cant even get the crit damage we would have to look at lowering the damage scores of big ships. would you really want to have to do every bit of damage on a ka'bin'tak with no crits?
bigger ships can just survive the hits longer and effect repairs.
it should be no harder to ever cause the actual crits, bigger ships just tend to have more back up systems and so can generally ignore the effects of the crits.
also under this save thing as you cant even get the crit damage we would have to look at lowering the damage scores of big ships. would you really want to have to do every bit of damage on a ka'bin'tak with no crits?