While a 1/12 flight speed would be a perfect scale speed I think you'll need to temper that a little with reality. A 7 foot span model will need to be built to a crazy light sailplane like weight to keep the flying speed down to even near to the mid 20's mph region. This may just not be practical.

And I also concur with the washout figures. You can't go wrong with lots of washout on a highly tapered wing such as this.

Good luck with an interesting project.