I found that the square of 2004 2500 standard roof was not at all where I wanted my vent. It was too far forward. I put the vent favoring the rear by cutting one partial rib out. Some have made up fancy spacers. I just beat down the rib and used sealant to keep everything water tight. Installation was in 2008. So far so good. vicThere was an obvious square spot over my rear bed for my Fantastic Fan on my 02. (Hole size seems standard in the rv industry.)
...Dan
I ended up using a vise grip plier for sheet metal (wide flat jaw) and crimped it flat after cutting slits in the base of the rib. Originally I was going to fold the top of the rib back and then fold over the flange but with the alum reinforcement strips I didn't like the way it was going. Used JB Weld on the inside where I cut the slits after I flattened it out. The reinforcement strips allowed more torque on the flange bolts to flatten things out even more and allow good butyl tape seal.I found that the square of 2004 2500 standard roof was not at all where I wanted my vent. It was too far forward. I put the vent favoring the rear by cutting one partial rib out. Some have made up fancy spacers. I just beat down the rib and used sealant to keep everything water tight. Installation was in 2008. So far so good. vic
https://sprinter-source.com/forums/showthread.php?p=37473#post37473
How to (with pictures):. Wish I could post some pics...