[1.0] Show bridge stilts?

[AileTheAlien]

I made a new bridge, that can be placed over soft sand instead of water, by copying / changing the existing bridge def, and the bridgable defs. I can get it working, and can change the graphic used for it, but I cannot figure out how to make the stilts / support-beams show, that appear underneath the bridge itself. So, my "bridge" just looks like a normal floor, without the pseudo-3D effect from the stilts. Is this hard-coded only for the existing bridge, or is there something else I'm missing in the XML?

[swampslug]

I'm no expert but as far as I can see the bridge supports are inserted via C# code. There is a test to see whether the props should be inserted which looks specifically for TerrainDefOf.Bridge.
If you want to get your new bridge to work as the vanilla bridge you will need to replicate the C# for whatever defNames you have specified for your bridge TerrainDefs.