Sorry for the wait! It fits snug and fits to the edge of the bag. I actually ordered the ‘Chanel Cerf Large 2’ size (one cup holder model) they had on the website and then emailed them to change the dimensions to my bag’s interior measurements. My samorga measurements are 13L x 4.2W x 5H. I realized their website standard was taller than I wanted (theirs is 8in tall) and it would cover up the Chanel tag on the inside and maybe be hard to get into the side zip pockets. But when I went to measure it I also found their length to be a bit longer than mine. They were very nice and made it to the size I asked without any additinal charge. It took a long time to ship 3 weeks but I wasn’t in a rush and didn’t mind.
About the tapering of the bag (wider bottom and smaller top).... I don’t have any issues with the sizing of the organizer. I think the felt is soft enough to mold to the taper plus with the shorter height I asked for, there isn’t as much of the organizer reaching the top of the bag where it gets narrow. Hope that helps!