Kirk, I think what the example CZ is showing is that the top strap is rolled down into the blank until the back of the action meets his starting reference cut.
I don't think you can drop straight down and still be able to jump undercuts. Also, if you inlet the top tang, then work straight back to bring your reference cut filled in above your lower nub, the tang will climb out of its inletting because of its downward pitch.
Maybe, try it out on one end of your poplar, and flip it over to try a different approach if needed. You may not need to make a pattern of your tang, but it could end up being a bunch of scribing, rescibing and spotting.
