Very nice for a first build Louis, and a great kit to start on. I built one about 10 years ago and had problems with the rear bumper fit also, but mine was related to the side windows. I rebuilt it a few years ago and cut the windows loose, trimmed them to fit flush, and it went together beautifully the second time around. Remembering to wash the body was something I learned the hard way, just like you did. It'll become the first thing you do eventually, but you've got to train yourself to do it!