I think that the rear section should of been lower behind the wheel anyway. Seems ever one i look at had a mild up hill flow to the lower side of the car. I found some pictures,Hare to find Buicks but olds has the same quarter lines and you can get the idea from them. I think a Cruiser skirt would save you a lot of work. Can you take a full side shot of the quarter and post it. You have some pics and they are chopped off. Would like to photo shop a set of skirts on the car.