I like the trick of no bottom, that’s a slick way to get some vertical height.
I looked up your fans, as they’re the real wildcard here:
In particular the static pressure rating of roughly 0.0039 PSI seems really low for smaller parts. I get that these were the parts you had lying around, they’re totally worth a short. I’ll be curious to see if you find them strong enough to keep parts from flying off.
For more on static pressure:
If you do find that your vacuum isn’t quite keeping pieces where you want them, I do like my air assist fan reducers…