There is an old video of O'Sensei using shihonage, I believe on a US marine. You should see the ukemi he tries to take.
It was an MP, and the ukemi he tries is worth watching.
(starting around 3:05)
IMHO, I believe when using Aikido on the 'untrained' your technique has to be very clear and strong, but not necessarily hard. Like working with a beginner in class but just a bit hard to produce your desired results. i.e. you may want to cause them some pain to give them a wake up call, but not an injury.
You surely will find this clip (http://www.youtube.com/watch?v=MyT5VUDoggY
) of Shioda Gozo very interesting, especially what can be seen from 0:50 until the end.