Spent a few days a year ago July in Isla Blanca (north of Cancun). The draw was mostly small tarpon to 25#'s but got hooked on chasing the permit. All the flies I had were crab patterns and relatively heavily weighted. Most all the permit we saw were trailing rays. The heavy flies invariably spooked the fish when you put it on their head. The third day the guide's son acted as our guide. He had a very small (#8) unweighted crab pattern using felt, mono eyes, rubber legs and epoxy. (He was an exceptional fly tier!!) Put that right on the permit's head and it barely caused a splash and they hammered the thing. Nothing big but my brother hooked his first permit on a fly, around 8#, and it promply ripped off at least 200 yards of backing!!! He is sure hooked for life!
Last day we both hooked but did not land slams. Very cool place to fish!!