I have. My bike came with grab handles so I removed them and fitted a BMW rack with shad box. Not that difficult to do but you do have to remove the rear panels to get access to the screws.
I didn't bother with the grey cover but did have to buy the complete pack of screws (Item no 4 on the fiche) as it was the only way I could get the 2 top hat spacers need for bolts underneath (item no 7)
w w w.online-parts.co.uk/bmw-bike-spare-parts/Catalogue_14000.html?fztyp=0J81&fztyp_mospid=60297&catalog_cat=77&bildtaf_btnr=77_0706&bildtaf_hg=77&year=2019&month=05#sub