Did that been there got the scars
The number one thing to remember is DO NOT TRIM ANYTHING UNTILL THE ENTIRE PIECE IS IN PLACE !!! I failed to follow this advice and will have to redo it with a new piece !!
Also, go to home depot and get couple rolls of the silver insulation for water tanks etc. Put this down first, it is cheap and effective, Cover ALL areas you can including the roof of the rear compartment (laughingly called the storage area) you will glad you did - good luck !!!!!