I asked Bill love about this and if I recall his answer correctly, the smaller oustalets from the northen part and the larger from the southern part of the island.
Correct. Philippe and Bill did a trip together and there is a Vivarium article documenting it, showing the different localities of oustaleti. I don't remember which of them was the author of the piece, but I think it was Philippe. Interestingly there is a picture in the article of what Philippe speculated (pers comm) was a oustaleti x pardalis hybrid.
Also, you can try to look up pictures of oustaleti from the west coast around Morondava if you want to see some true giants. They are much more heavy bodied as well as longer in length. I remember seeing a huge male at STF that they had imported. Still the biggest/heaviest chameleon I've ever seen in person.
Out of curiosity........... Ambanja (Blue Diamond) is that his name or a special color variation of Ambanja in Europe? Cos i have been seeing blue diamond Ambanja at Europe forum. Kinda Curious!!