Pressurized dumping to allow dumping at higher altitudes looks like a definite plus and necessity for this airframe. The plane isn't going to operate out of just any airport though, so those higher travel speeds will be needed to make up the difference. Washington State has a perfect airport for it at Moses Lake though. Japanese Air Lines trains its 747 pilots there all the time. I once was visiting some family who lived not far from Moses lake and was shocked one morning to hear/feel 5 747s flying close formation fairly close to the ground, go right over the house. I was baffled by the spectacle until somebody told me about JAL.