Good. 80" is a lot better than the initial 60" that you were talking about. That book and wood sure arrived fast then...
As far as dimensions go, a hickory backed osage ELB will not be too different from a yew ELB. I'd go for 1¼" wide for around 60#@30", tapering to ½" nocks. Length of about 76" (72" would work as well, but since you're a beginner, some extra length will give you more leeway). Thickness about 1" at the handle, tapering to ½" tips. This will be a bit too thick, but it's a good number for roughing out, from where you can start floor tillering.
How thick is your hickory backing? And did you glue it yourself and what glue was used for that?