Nasty ain't it? Hey, save those plastic edge anchors from the factory carpet, and install them on the new carpet after you cut the edges to size/fit. I have even used to Mazda staples that they used to fasten them in place! Works like a charm!
Show us the completed new carpet install!
Here is a couple of pics from my 1993 Regular Cab 4x4 truck when I put new carpet in it.....
I left the carpet long at the rear of the cab, and cut relief cuts where the humps were, and it is sandwiched behind the factory rear wall carpet and B-Pillar covers that I installed also.