I always thought that 4 racks seemed a bit skimpy. There seems to be a lot more room in there that could be used. One day while in Cabela's I saw they had a 30" model called the Sportsman Elite. The main difference seemed to be the space for 2 more racks.
So I called Masterbuilt to see about ordering the rack holders for that model. It was a huge hassle because their customer service was fairly lacking. The rep seemed very annoyed that I would try to circumvent the 4 rack system by buying other parts. She made it very clear that under no circumstances would I be able to return the product since I was basically breaking the law and upgrading my own unit. I accepted the warning and it cost me $25.
Two weeks later it arrived. They sent me another 4 rack holder set like the one that's already installed. So I called to get it straightened out. The guy on the phone told me I couldn't return it since they warned me several times that it wouldn't fit. I told him that's fine but they shipped the wrong rack holder. He reads the notes, "Customer wants the 6 rack unit, I told him no returns and he agreed. So sir, we can't accept your return." Now I am getting annoyed so I asked him to read what part they actually shipped. He says, "4 rack unit." So I said if they warned me about the 6 rack, why did they send me a 4 rack. He was flummoxed. So he has to put me on hold and after a while comes back and says he will ship out the 6 rack holder that day. I asked what to do with the 4 rack set and he said just keep it as it's cheaper to let me have it than pay to ship it back to them.
So another week goes by and no product. So I call them up to see what's going on. The lady on the phone puts me on hold to research it and she finds that the order was placed but somehow never shipped. So she agrees to make sure they send it today and put a rush on it. I requested 2nd day shipping, she said she would have the supervisor do it. Of course, they don't send it 2nd day mail, they ship it the slowest route possible, so over another week later it arrives.
It didn't fit the same screw holes as the original racks. So I removed the old ones, mounted the new ones in the bottom screws which did line up, and then made 2 small holes for the upper supports and screwed them in easily. Then I put in the other two screws where the old rack fit to plug the holes. It took about 5 minutes. Now that I have those extra racks, I may cut one up and try to rig up a single rack between the bottom two for 7 racks total.