You should be able to add a .onion relay. 

I havent dont performance testing, and tor is notorious for being under attack perpetually. 

Lmk what you find 🙏 

 I was just curious. Where does one find .onion relays anyway? 😅

Does Damus have one for example? 

 Great question. Check the damus github for the tor issue, @BenGWeeks profile, and maybe nostr.watch