These may help with the initial guess on how much rye to use:
- Brewing with Rye: Tips from the Pros - Brew Your Own
- http://allaboutbeer.com/article/rye-homebrew-recipes/
- Beer Here: Canoe Paddler Kölsch-Style with Rye from Leinenkugel's - Isthmus | Madison, Wisconsin
edit: should have expanded the search criteria to “rye kolsch” earlier: