leaks in the rt. rear flor area that you can't see are also caused by clogged drains in the wheel wells and a hole rusted under the battery tray. My 300 would fill up that way and I thought it was window seals but it wasn't. Cleaning out the wheel drains helped but in a real hard FL. thunderstorm the rt rear still would fill up. I pulled all the carpets & seats off that side and turned on the hose. Water was coming under the floorboard near the front and running down the channels the vac lines are covered in. Then I found a small hole under the battery tray after removing it. Cleaned it out, filled it with spray foam, and bondo/paint and the leak is gone.