Looking good Bob.
Did a little bridge work today myself. My 5 foot outdoor lift out was made with a plywood deck and 1x2 lumber about 5 years ago. It started to sag after about 3 years. Last year I tried to level it back out a bit, but by spring it was sagging again.
I picked some heavy gauge 2" x 2" square aluminum tube out of the junk at work last week. In about an hour with 7 passes through the table saw I had a solid metal girder to replace the sagging wood bridge. A fresh length of track was laid over the top to test and it works great.
I sure would like to do the nice bridge ties like yours, but I don’t have the patience to spike it. Maybe I’ll put some long ties between the tie strip ties. Going to the hobby store tomorrow to find some .125 angle to simulate plates on the sides.