Motor Box Upholstery

[Larry E]

Here are a couple pictures of my motor box that I am upholstering. I did not have any problems with the top and front but the sides are posing a challenge in getting the puckers out especially where the angles are on the front. I have installed the beading along the edge and have the small strips of card board that help keep a straight edge when the material on the side is stapled on from underneath the material. I have cut the material for the sides oversized but should I cut it to shape on those angles? If you have done this before do you have any hints?

Thanks
Larry E