I can't speak for Bamse, but that rear floor can be a huge PITA to get a big exhaust around if you're super low. Cutting into the floor there lets you tuck it up way higher.
Also it looks cool.
Yes, i had some problems with the height of the exhaust, and the easiest way for hiding the silencer was actually to pull it up in the rear passenger foot space and, well.. eh.. out of the door. Had no usage for the backdoor anyways.
This year is the exhaust system gonna be a bit smarter(?) pulled, yet something in the brand of Bamse.
And it certainly looked sexy! 8)
//B