In #14, I like the integration of the design vee above the SDL, but would like to see if can be a little more prominent and be clearer that it is the design vee (perhaps the arrowas again". The "D" looks too close to an "O". What if the vee went through the D? Hmmm...
In #15, I still like the vee element being a bit more prominent now. WHile simple it goo, it's still not clear that it represents anything, so incorporating soem arrow elements may make it better, open up the vee some (so it does not go so low), and maybe make "cross arrow" element part of the "D". I like this "D" better.