Well, here are some more pics!
Here's how I went about adding the taper to the core lam. First, I made marks to divide the working part of the core into 4 sections.

I extend those lines to the sides. Then I mark the thickness I want at those lines. Since I'm going from 3/16" to 1/16", I make a marks at 5/32, 1/8, 3/32, and 1/16.

I then get close to those lines using the spindle sander, trying to make an even roughed out taper between the lines. After I get close, I finish the rest of the taper by clamping the lam to a table and trimming it with a hand plane.

Here's the end result:

And here's what the flipped osage looks like:

I'm getting close to glue-up time. I'll probably do it Friday after work. Jandersson, I laid the bow out so the handle/riser section is offset from the center of the bow (the middle of the handle section is 1/2" from the middle of the 68" length). I'm not sure about moving the handle section around if you didn't plan on it being offset.