For trapeze in Revit, we are using support specs to drive rod size and standard washer and nut counts. Separate ITMs for 1/2", 3/8", and 5/8" rods, and another using gripple cables.
No product list necessary for trapeze. just set options to Pipework = No and Oversized = Yes and Use Support Settings = Yes.
Support specs should include:
Ancillary Materials: Strut (Apply to Bearer)
Support Rods: quantity 1 (Revit automatically doubles for 2 rod supports like trapeze)
Fixings: Hex nuts (quantities for single rod)
Clips: Square and/or flat washers (quantities for single rod)
Apply the support spec to the ITM properties (See attached image)
The ancillary kits are used for overriding rod size, changing nut/bolt counts and sizes, and adding various inserts (bluebangers, beam attachments, etc). Don't define the ancillary material for the strut bearer in the kits. That is defined in the support specs and the kits override rods only.