I too found the Navy Grog lacking in some depth so I added a Barspoon of St Elizabeth Allspice Dram.
Excellent idea. I too do that with tropicals that I otherwise find lacking (like my "Piña Colada," which I make with dark rum, added lime, and a barspoon of allspice dram). In some cases, a small amount of a pie spice amaro (Ramazzotti, etc) can similarly add depth and spice; I like Luxardo Abano, which has a cola character but adds a great savory black pepper note.
My favorite Tiki drinks tend to have a depth of spice to them; it's one reason I generally prefer Don the Beachcomber's drinks to Vic's (as much as I love the glorious Mai Tai).
Can you give your recipe for the Mai Tai?
I've been studying Wayne Curtis' book, and a Bottle of Rum. Curtis' Mai Tai (which I think is derived from Trader Vic's) is 1 oz Jamaican rum, 1 oz medium bodied rum, 3/4 oz orange curacao, 3/4 oz lime juice, 1/4 oz orgeat.
He also lists a Don the Beachcomber's Mai Tai as: 1 1/2 oz dark rum, 1 oz medium bodied rum, 3/4 oz lime juice, 1 oz grapefruit juice, 1/4 oz falernum, 1/2 oz triple sec, 2 dashes Angostura, 1 dash Pernod.
I'd also be interested to see good recipes for the Zombie. Does anyone use real absinthe in their Mai Tai or Zombie formulae?