Hello.... sort of new to the hobby, and very glad I have found this place. I have a suspended track layout in my home, which happens to be a duplex. The plan covers 3 rooms and a hallway. I noticed the other day when a train passes in another room on the adjoining wall it is very loud. One of the walls where the trains pass is the common wall shared by our neighbors. I have foam roadbed on that wall but the neighbors have said they can still hear it, if only for a few seconds at a time. I would like to make a bridge that spans the whole wall so that I do not have to have the shelf attached to the common wall at all. Of course I could just run the shelf from one wall to the other making a bridge, but I was thinking more along the lines of a ("pass thru"?), type. The bridge would have to span about 15' . I have modeled several small bridges of wood and styrene, but how does one start such a long bridge? Any ideas? I can soon post the pics if anyone thinks it would help.