Your Cody sounds so SWEET! And so lucky to have such a lovely big backyard! We rescued Maggie about 4 months ago, she has made great strides in that time. Its so funny, we too have a large grass yard, and maggie still just races around on the concrete patio! Silly girl, I keep telling her the WHOLE fenced yard is hers for the taking!
Anyways, just yesterday and today I kept her out 10 min instead of 5 and she did eventually go and we only had one accident (and that was when our neighbor came over and she got very happy and excited hehe).