Hi, yes it can be done.
By default RailClone doesn't allow to modify the default presets, because the changes would be overwritten by updates of the software. So, first you must create a copy, and then modify it. In this way:
1) Open the Library Browser.
2) Create a new folder in the User's Library
3) Select the library you want to copy, drag and drop it over the new folder.
4) Select the element to modify, right click->Properties
5) Take note of the 3D Model->Max file
and Object's name
, where is stored the preset. Close properties.
6) Select again the Library in the left side, right click->Open In Shell
. That will open the folder which contains the Max scene.
Now you can open the scene, locate the RailClone object and modify it in the usual way. Basically the Library Browser works copying the style from an existing RC object.
You also can locate and copy the Max scene directly, or create a new Library using it. You can find all procedures in the Browser Library documentation
I hope that helps.