Anyone ever spray clear coat over duratex?

I have found that undiluted Duratex has more than enough sheen and (given enough time) toughness to handle my needs.

What specifically are you after? I suspect that an overcoat of clear would A) not let the Duratex cure and/or B) bring more sheen than I would like. And possibly C) clear coat spidering with movement.

You may want to use clear bar-top epoxy, so that it will at least have some endurance...
It's not gonna be piano gloss since durtex has a texture, but it will be shiny-er.

I checked the data sheets and they say nothing about top coating, so I doubt its advisable.

That being said my recommendation would be to contact the manufacturer directly and ask. Only they will know for sure if this is advisable, and if it is, if a particular form of clear coat (i.e. epoxy/lacquer) is the best choice. Some coatings can cause other coatings to fail so its important to get the chemistry right.

There is a contact form on the web site: https://www.acrytech.com/product/speaker-cabinet-coating-duratex-spray-grade-black-1-gallon/