John, affected coaches are all over the board from 2000 thru at least 2007 shells. You can read all the threads and see that there appears to be no common factor. Because the so-called Final Fix(no see em rivets) has turned out in a few cases so far not to be final, We decided not to participate in a “crap shoot” and go from a rivet XL to an H rather than an XL11. The H series X chassis is the same as the XL11, and even though we like the looks of the XL11 better,we felt more comfortable going with the H. Geo