I used both rubber pads in each location. Underneath the spring stack there is very thin rectangular piece of sheet metal that doesn't appear to add any thickness, not sure why it is there. Is this a type of slip sheet should I mount them with out the rubber insolators?

I'll look at speedway motors to see what they have. Any negatives to not having the rubber insolators? I was thinking about getting away from them. Without the rubber insolators I would think it would be easier to lock the pieces together