Yeah it looks like it's going to be too wide, but you never know. Because the bottom part of the back and chest connect and not the top, that's where you should work from to fix it. In other words, you should line the bottoms up and see how it looks, and possibly post some pics for us to see. Depending how it looks after you've lined the bottoms up, one option is to make adjustments where the bottoms meet. You could either trim down the paper at this stage, or you can go on with fiberglassing and fix it when you get to that point. My suggestion is to go ahead and fiberglass both pieces and fix it then. The reason I say that is because if you start to cut and trim your pieces now, you may put too much pressure on them and they could warp in their flexible paper state. Fiberglassing the pieces would make them stronger and resistant to unwanted warpage when you're trying to make the bottoms line up. The great part about trimming it down in the fiberglass stage is that even if you mess up a little bit you can fix it once you get to the bondo point. That's just what I would do if I were in that situation. Again, if you line up the bottoms of the pieces on the dummy and take some pics, we can get a better view of exactly how far off everything is. Also, if you import the chest and back into one file, you'll see that the chest does stick out slightly further than it looks like it should. So it really just depends how it looks when the bottoms are lined up. Hope this helped and I can't wait to see more progress! Feel free to pm me with any questions or anything.