Possessive forms of words ending in -s

[platypeanArchcow]

This is probably goofy, but in a situation like that I will say the word (possessive form) and if it, to me, sounds like there's an extra s sound on top of the ending of the base word, then I'll tack on a 's, otherwise not.  (Option 2 is my default).

So you're saying that you'd say "Congress's", because the s is not an ending, but "Stevens'", because that s is already a possessive?  That makes sense to me.  I may do that sort of thing unconsciously.