The is a view down the aisle that shows how far it sticks out. It is above shoulder height so the average person (less than 6'6") will just have to move his head laterally. The bridge will go from that clamp to the long 2X4 that is on end, holding the roadbed. There will then be a shorter deck girder to complete the bridging work.
Here is the view from the other side. I am beginning to get concerned that the weight of the plywood nose is too much as it has quite a moment sticking out so far. I may make another one from 1/2 inch plywood. That should be much lighter.
Here we are looking down. I am going to face the whole thing with the flexible plywood that I use for the facing member of the benchwork. I have to build some benchwork inside the current framing to tie it all together.
Here we are looking up from the bottom. I think that I do not need as much strength as the 3/4 inch plywood provides so 1/2 inch would do fine. Perhaps the easiest thing to do is to build it and then compare.
A last close up. I have the C clamp on there to hold the plates while the glue sets. As I look at the picture, I see my last moving project, moving that bookshelf to make room for Shamokin. The civil works are drawing to a close, thankfully.