Per Theo Clark's comment below, I made with 1.5 oz of Appleton Estate and 1/2 oz of Plantation overproof rum. An extremely well-balanced cocktail, both in between sweet / sour and gentle / boozy. I also doubled the sugar syrup as mine was 1:1
Like others, a little too sweet for my taste. Might try increasing the tequila to 2 oz as it was understated or decreasing the pineapple juice a tad. Overall, a nice variant the traditional margarita.