A bit late for the OP no doubt but just to help others who might read this:
Yes for sure you can hook up and load up and go flat out from the start, and you likely won't have any problems that show up in the first few hundred thousand miles. These trucks are tough.
Or alternatively you can be gentle with your complex and expensive new machine, and treat it the way its manufacturer recommends, even if that means a few days' inconvenience.
Hmmm. Tough decision. But each to their own and it's your money.
Remember that there's more in the drivetrain than just the Cummins. I understand that the main reason for the manual recommending gentle break in is to bed in the diff. (And how come some people will quote one part of the manual, and ignore the other part? Must be written in different ink or something.)
If your Duramax buddy is such a twerp that he doesn't understand that heavy duty moving parts need to bed in, there's probably no helping him.
