SLO - as we have a 2015 Sunstar, I'd love to see the mods you've done. Not that I'm planning on any, but you never know.
If you've seen it, I have a shower problem going now posted in this same newsletter.
To the OP. Although ours already came with shelves in that area, not cabinets, we solved the problem differently. The shelves have a small raised area in the front to keep things from just sliding off. We just use medium+ sized good plastic bins with lids for l/s tee shirts, sweaters, sweat shirts, light jackets etc., but the could store most anything.
We, personally, don't mind looking at the bins at all and it was instant storage. Further, while they may seam insecure, not one has even moved, much less fallen in about 15k miles of all kinds of roads.
Good luck - post pics when you're done.