What a coincidence--I make dog collars, leashes, tracking lines as my business and I also have a tracking dog named Chloe (Standard Poodle), (and two other tracking Poodles, Myles, and Calypso). We do not do blood tracking. Rather, we track human scent in the field and also do Variable Surface Tracking in various urban environments which involves tracking on concrete, asphalt, and other non-vegetated surfaces in urban settings.
When I track with my dogs, I use a harness and a long line (30-40' in the field) and 20' in the urban environment.
I was wondering whether blood tracking is done with a harness and long line. If you do use a harness, you should make a harness to match the nice collar you make for your Chloe.