Thanks for the comments, I'm aiming for a base pitch (chamber tonic) of C a=440, do you have any pictures of your own ocarinas? Ocarinas can be played as both a transposing or non-transposing instrument, the note intervals are generally the same.
The base pitch of an ocarina is primarily determined by chamber volume and blowing pressure, the former must be sized so that the ocarina plays in pitch without excessive breath. It is possible to vary this somewhat with sound hole size, or by drilling a tuning hole, however they do reduce the maximum achievable range and weaken the high notes. No