That looks good and using flat steel certainly takes less space. I see 2 additional mounting points under the seat?
Givi makes great stuff.
I bought the Honda rack. It has a good large surface to lash a bag as I'm trying to avoid a top box. I thought it would be at least powder coated but I believe they just used paint that scratches too easily.

 

Yes it's well made, paint is thin though, the bracket just rests in the gap between the seat and frame and doesn't interfere with the seat being taken on and off and Givi supplies some foam strip where bracket rests on the frame. I think for £78 it's a good buy plus the cost of the chosen plate, monokey or monolock.