I hadn't seen this thread before, but I've seen that bumper design! 
When I was trying to figure out what to put at the end of my turntable whisker tracks, my eyes fall on all the left over Gargraves ties from laying the track. Drill a hole, put a screw into it, and you have a perfectly functional bumper. 
The jumper across the back ties the two outside rails together, saved me from having an extra drop, for the whisker tracks I wanted both outside rails live for reliability.
