Well, I'll post three pictures, then. I personally doubt that a real size for the islands cans be determined simply with the types of shots we have, but I guess having them on hand wouldn't be bad.
This is the video I viewed for these shots.
This image is the first one, where Rathalos is flying away from the edge of the island, and we can see a decent amount of the land that makes it up. Not too much to report with this image, though.
The second image here shows a good view of one of the mountains on the island, and it seems to be a sizable one at least. There appear to be more like this one on the island, only they are blocked from our current view (We'll be able to view them in the next shot).
This third and final picture shows more of the mountains, and other, smaller mountains in the distance. It also shows a great amount of the island in front of the Hunter. This shot is available from on the mountain in the second shot, where the Rathalos is flying towards it.
All in all, I don't know how someone could calc the size of the island and force it to sink or anything like that, but hey, it's nice to have
something on hand. And, given the size of everything and how it was all easily threatened by Ceadeus, I think Island level is a distinct
possibility, but I guess I could be wrong. :/