You can see the rest using the api and ?page=
-->> http://api.twitter.com/1/statuses/user_timeline/shitmydadsays.rss?page=3
You could also use ?count=200
The max is 200 though.
You can only go back to the last 3200 tweets, so it's probably easier to just random 1 to 3200 and divide by 20 to get the page number.
Edit The guy only has 104 tweets ;/