Hahnemuehle Photo Rag Metallic is a very difficult paper to soft-proof. I don’t think any current software’s soft-proofing capability can replicate the luminance shift and color perception changes of this very specialized paper. For those of you who have not printed on this paper, don’t think “metallic paper” as you are accustomed. It is VERY different from the typical metallic papers. One of the things I’ve learned is that it’s best not to try to over-soft-proof this paper. Getting the proof preview to look like the screen representation of the image, usually results in a terrible screen-to-print match. I’ll often only do a very minor increase in contrast, and a minor lowering of the black point on my first run. The “proof preview” will look very poor, but the print will be fine.
Paper-white is actually a kind of champagne-silver color. Impossible for software to replicate in soft-proof. Colors tend to fluoresce and gain in “apparent” luminance in the print (the opposite of what one normally encounters). It is a very specialized paper, but for those images where it is a good choice, it can be stunning. I don’t think the OP’s image is a good choice for this paper.
This image looks spectacular printed on this paper:
Rand