To bounce of what Nick mentioned - we didn't have a software program for our pack when we went to China on tour, but we did a pre pack plan before we left the US. However, when we got to China, after Shanghai, every other city provided us with the most unbelievable trucks - nothing we could have ever prepared for or mapped out. (One was a refrigerated meat truck - with hooks coming out of the ceiling!) I second Mac's suggestion - but like Nick said, be prepared for stuff to just not work, because when it comes to reality of what can be lifted high and what can't, etc
Sometimes you can develop an even better pack when you're packing the truck. Sometimes things make more sense when you're in the moment, though I know that doesn't help with planning for beans.