a plaring pic would make it easier to tell. with the tail relaxed like that its a bit harder to tell.
i had something similar, i bought a SD off ebay and i was contend he was a SD.. untill i saw him flare flly about a week after i had him, and he streached to a half moon. he has since grown alot and his tail gets "bushyier" all the time, he wont sit still so i cant count is rays easily, but his tail just seems to get bigger all the time, and he has even doveloped a bit of "feathertail" but i dont think this will spread right along his tail, its only on one bit of his tail.