back bone and new inset shelf panel

The original model is great, but i was getting a bit of sagging of the right side of the model once installed. This remix takes the shelf insert and adds a supporting backbone in the back and the backbone model. how to fit: install the main surround, slot the backbone into the insert, slide the backbone into the main surround and slide the insert/backbone left to fit, click in the central brace piece. dissaembly: use a hefty chunk of blutac and pull the central brace off, repeat for the insert from the right side. Printing: I printed the backbone at 50% and 6 perimeters, the insert was 15% infill and 5 perimeters.