Mixed Drink Proportions - Help! (John's Special, Cabo)

I had a drink called the John's Special at Pancho's in Cabo San Lucas.
John is the proprietor, and a tequila maven, and it's a very nice drink. It's described as orange juice, lime juice, tequila, brown sugar (I'm thinking it's turbinado) and soda. The drink is moderately sweet, rather sour, with a decent kick and no noticeable carbonation. There's obviously not a lot of orange juice, as the drink is pretty clear.

If I were to make one of these for myself, any clues or rules of thumb as to proportions?