Engine as RBE2 elements

Hi,

I am modeling the engine of our frame as a rigid element. I thought of creating RBE2 elements linking the 4 nodes (see the image) :

- 'calculate node' as independant

- 'multiple nodes' (selecting the 4 nodes) as dependant

Of what I understand, the 4 nodes will now be fixed from one another, like a rigid plane. 

Is there another method ?

I also thought of another option : creating a rigid 2D plane. I don't know what would be different... But if you could explain how I can create one with these 4 nodes, it would greatly help.

Thanks,

Ben