I have an 11' Nalu with a mast base insert and it's position is 2m (78") from the tail.. I think the same distance from the tail on your 11'6" should be fine.
The old 10'10" Nalu worked well with a sail but you might need a better (pointer style) fin than the standard dolphin style fin that they come with..
Like this fin that I'm using in this old vid of mine.
