EDIT: RobSoundTrack also made a fixed version of the Nimaid Ocarina -
his is available here - https://www.thingiverse.com/thing:2755765
More EDITs: There's also a lower pitched version of V17 in the works: https://www.thingiverse.com/thing:2810366

V.6 SoundSample:https://youtu.be/6W6-l9NYwsU
V.10 SoundSample:https://youtu.be/FJdEca6Ykgg
V.17 SoundSample:https://youtu.be/Mz09SC4Y4mc

Version Notes

• V.1: High notes work, but are still airy.
•V.6: Angled mouthpiece and decent high notes. Sound sample included.
•V.10: Voicing wildly beaten to death. Ocarina is now more in tune to C5, but higher notes are still out of tune. Seems quieter. I might be mental.
•V.17: Voicing completely changed again: Tried to more or less recreate the shape on my clay ocarina. I have no idea if I like this one more or not. It is closer to being in tune.

Summary

The original model is amazing, but I had trouble getting the highest notes to play.
After a bit of research (https://www.youtube.com/watch?v=vFuYeW_OxEg&t=204s - I decided this was a #3 C Ocarina. May be wrong.), I found that the voicing needed some slight adjustments, so I did a quick and dirty modification to get it working.

Since then, I've kept trying repeatedly to rebuild the voicing to get the high notes to perfection. I'm still not there, but I think it's improved some.
The tuning is also much improved, but I think still a little off on the highest notes.

Originally, I had made the airway exit more narrow. The tighter airstream should assist the reverberation of the instrument.
The labium lip is now further away from the windway exit. This should strengthen the high notes, and make the lowest note harder to blow out with added wind pressure.

In every version I tried to leave the voicing rounded, as I like the softer sound a round airway creates compared to the sharp sound a rectangular one makes. Tried to make the ocarina a bit quiet, but if anything I think I made it louder.

Until I finally printed one in wood - for whatever reason the windway feels smaller (it resists breath a bit more than the regular plastic ones) and in turn appears to have gotten quieter. Perhaps the secret to a quieter instrument this whole time was simply to narrow the windway some more?