I'm not sure about that. I know that when I set all this up on my phone, in China granted, that I had to set size limits and things of that nature that were in alignment with the carriers size policies.
Honestly, your best bet is a good ol' fashioned 2 hour long google search on this topic. Most people here aren't going to have great info on how to help you with this specific situation - furthermore this really isn't a hack. Maybe try the broader iPhone forum - feel free to stay and keep asking, but you might be barking up the wrong tree w/ this one.
It took me about 3 days of searching google to figure out all my MMS settings. Furthermore, it only works on YOUR phone. If your buddies don't have their MMS settings setup, then it's kinda pointless.