So looking forward to trying this! I just returned from the store with a 7 1/2 pound whole chicken (yikes!)...any thoughts on the timing for this...

Probably not much different from instructions as given.
Authors specify "8 chicken thighs (or 1 whole chicken)."
Web sources say average chickens sold in USA prepared for cooking (without innards) weigh 1.5 to 3.5 lb (broiler), or 3.5 to 6 lb (baker).
So it's either double the size of the smaller ones, or just over the larger one. You may want to have more aromatics around and decided how much of them to use by sight when prepping the bird.
Either joint the chicken, spatchcock it or roast it whole, to same directions given...times, outer (browned ) & inner colors (not pink) and internal temp when done (165F or 75C).
Most important, they want you to start cooking in a heavy lidded pot, with enough space in it so there is air around the chicken pieces (too close and they are almost stewing instead of roasting).
Do you have or can you borrow one very large or two medium size dutch ovens for this?
If yes, good luck and let us know how it turns out.
If not, maybe consider a more traditional roasting method for this bird, and save the cold-oven technique for a smaller bird you can accommodate in covered pot(s).