The nice part about this store plugin is that every item called by items.txt does what sm_downloader does, except only for the items you require. Basically, you don't need sm_downloader for this plugin, you're only making your clients download more items than necessary.
Edit:
https://github.com/dvarnai/store-plu...re/hats.sp#L99
You can see right there it's calling a download and precache for the specific items you've specified in items.txt.
Edit 2: Looked a little bit more into it
/models/store/hats/ is simply a rough duplicate of /models/gmod_tower/, however with a couple extra items and a few extra items missing. I'm assuming the models from /models/store/hats/ directory calls textures from /materials/models/store/hats/, meaning that's not quite a duplicate. If you use only the models under /models/gmod_tower/ then you don't need /materials/store/hats/ directory.
You can delete any .vtf and .vmt file inside /models/gmod_tower. Other than this, everything seems to be set.