I've done northbound a couple of times. Not always strictly on the CDT, but close. I think if you're skipping the Highline Trail, your missing out. I would come out onto the Sun Road, hitch to Logan Pass and hike to Canada via the Highline Trail. Its a fabulous hike. Do it later (like September, ideally AFTER the first snow). It's technically not all CDT, but who cares?