A charcoal-filtered light rum works best as more full-bodied rums simply don't sit well with the cardamon. Hit the right balance with the right rum and...
I love cardamom! I muddled 4 pods instead of 3, and threw in a few extra dashes of cardamom bitters (Scrappy's), but I didn't end up with a strong cardamom taste, more like scented. Next time I might scale back the lime and really go for it on the muddling. This was a great use of the Scrappy's bitters -- they went perfectly!