Please be sure to do a "headliner" search on here for all of the prior posts on this subject. I don't have any specific knowledge regarding the Grand Coupe (others likely do), but if the 5th bow does not fit between the clips, I would think you could evenly grind it down to fit. If on the other hand you are finding that the headliner it's self does not fit, that would be due to the sleeves on the aftermarket liners are too long and you just need to snip (very carefully) a slit about 3/4" in to free the bow sooner. Once you have the 5th bow in place, the whole idea is to square up the liner and then attached it at the front windshild area, stretch & attach it to the back window and then streatch and attach it at the sides, being sure to keep your corner points square. Hopefully, you considered installing a sound deadner such as FatMat along with insulation (the thick carpet insulation works great), prior to installing the headliner. Best!