Hi Dave and welcome to the group!
I think you are wise to stick with you original choice and go for 11strings as it is quite a learning curve. If you haven't heard some of Goran Sollscher's recordings on 11strings do check them out. In my view some of the best guitar recordings of both renaissance and baroque lute music. As it to your choice of 11 string is it possible to give us some more info on the scale lengths? On the face of it I agree with Sylvanig in that the guitar with the least fanning would be easier to adapt to but there is always a trade off in that the guitar with more fanning and a more pronounced multi scale effect might sound gorgeous.
Good luck!
Bill
One caveat ... once you buy some arbitrary guitar, you are stuck with it and may have to hassle selling it.
I sure like the alto-guitars on the Heikki Rousu site that was just recently put on the front page of this site on the upper right (I can see it as I type this message). Both his and Roger Stromberg's appear to me to be the best bet. Look under Links>luthiers.
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