?

You don't need the entire plastic part, a big part is only there to be able to do the molding. Instead you need to cut the wedge-shaped parts from the strip and place them under the tank tracks. Not sure how the wedges are fixated to the car floor.

The main intention here is to look prototypical, not to necessarily to fixate the tank during model railroading (it might be ok though, I just have no experience with this kit). For that purpose I have made my own parts using a 3D printer that just snap on various flat cars: https://www.thingiverse.com/thing:2848819