I'm working on making a storage trunk that fits with the rear seat installed. I used the exterior dimensions of the Tuffy Security Storage Trunk. Exterior Dimensions: 9 5/8L, 33 7/8W , 11 3/8H. I'm going to use 1/2 mdf. I will most likely carpet the finish product. I have the correct dimensions of each piece. I have not yet decided the locking mechanism. Top: 9 1/8 x 33 7/8, Back: 11 3/8 x 33 7/8, Front 10 7/8 x 33 7/8, Bottom: 8 5/8 x 33 7/8, Sides: 8 5/8" x 10 3/8. I'll post pictures of the build. I know it might not be as secure as the Tuffy 16 guage steel storage trunk but I can't see myself paying $300 for it. Why not build my own. If someone wants to get into something bad enough usually they will. If it is out of sight they might not risk breaking in.