Hi Raymond,
I have fished Kadavu in the past , the doggies are hit or miss in the location due to the far distance from the lodge and the weather condition, Luke will be running trips to Papau New Guinea to target both species and I personally had a great results on his trip recently, if you are interested get in touch with him directly and if you are considering to fish Raivavae I don't think you will be able to get much information as we were the first group that fished the island for GT's and Doggies, if you are interested to fish Raivavae you can get in touch with us directly as we will be running trips on a monthly basis beginning of October 2014 till the end March 2015, good luck.
Tight lines
Sami