After checking multiple times the installation manual and the order of washers to install, the so called Top Plate slides left to right.
I called the Pan America service person at my dealership, and he said he got the same thing.
while trying to screw down more, I shot a screw head.

As anyone else got the same issue? It is really annoying (even though I have not taken it for a ride yet).

 

They are meant to move.

(Disclaimer - I don't have the top case, but this is what I have read. EDIT: this was about the aluminium cases......not sure if the Sport case uses the same principle)

 

They use the same principle. Purpose: stabilizing the bike's tail in buffeting wind situations. There is also a rubber dampener in the rear section as a soft limiter.

Anyhow, after 8000 km it starts to rattle with every small bump on the road. I tightened it a bit more, but I am at max mechanical torque of the 4 screws. I think I replace them with 4 car exhaust rubber mounting dampener. The golden engineering solution would be 2 lateral guide rails without backlash and hydraulic dampener (who is no one willing to pay I guess).

I feel a certain difference when I ride with the Sport top case vs without. I would definitely not fix them hard.

 

I mounted my Shad topcase so that it doesn't move, with no issues. Just an FYI, Shad makes the Sport luggage for HD. I wanted the expandable top case. It goes from chopped to HUGE!

 

Those bolts that fasten the plate to the back are made out of pure butter, I think. They are however, designed to move sideways, on purpose. Let's trust the engineers, otherwise what are you doing riding this bike in the first place...