See link here for pics, so you have a good comparison.
http://www.fas.org/man/dod-101/sys/dumb/mk82.htmI think its a fun idea, but if I am going to carry bombs on an aircraft in a simulator, I want it to simulate carring 500 lbs per bomb, as well as the change in flight behavior after the payload has been delivered. I love B-17's personally. Used to fly one all the time in FS9. Its such a great design.
You can try using the SDK to develop your own missions, using what ever aircraft you want, I suppose, even imported ones.