Well I was fiddling around with Beertools.com and trying to read the BJCP guidelines at the same time. My recipe was 100% compliance with the Kolsch style.
I have the following....
10.8% White Wheat
74.3% Liq. LME
14.9% Dry LME
Like is there a point where adding specialty grains for color becomes too big simply for an extract brew?
On a pound for pound basis, I think the 15% max suggestion might be a good guideline. A standard 6 pound DME batch probably shouldn't take more than a pound of crystal (one-seventh) and even that can be too much, though it varies per style.