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I'm "dialing in" the six bamboo elements of the core for the big bow - literally using dial calipers, measuring thickness at 3" increments for each of six 102" long pieces.

I'm actually kind of impressed with the uniformity and low total-length deviation I acheived using a hand-plane - on average the TLD is under .050" and various dips and bumps are +/-.010" and under.

(for reference: a human cranial hair is, on average, about .003" thick)

not good enough, I'm afraid, but enough to impress me ;)

I'm currently sanding down each piece to get uniform thickness (+/-.003") over most of the length with a mild taper (-.020") at each end.

stacking the six, and assuming the minor irregularities tend to cancel each other out, I'm hoping to get uniform stack thickness of .900" +/-.005 with total tip taper of -.120" over the last six inches or so.

Final shaping will be done on the hardwood core-cladding elements which will sandwich the bamboo core stack. I might fatten the stack with an additional hardwood strip right up the center, but might not. Depends on what feels right in my hand, I guess.

Once all the core pre-shaping is complete, I think I'll cheat and pre-glue and pre-bend the total core stack before adding the back and belly bamboo. To do this, I will need to make a rigid bending template. Fortunately, I managed to unearth my copy of "Arms and Armour of the Samurai" and find a good side-on photograph of an un-strung bow, illustrating the curve pattern. It is now simply a matter of scanning that image and figuring out how the curved length translates into linear length, scaling it to match the 102" I have to work with, and plotting the template.
Then... time for more sawing and sanding. Pine ought to do for the bending template, so it won't be too nasty a job.

The reason I'm considering pre-bending the core is a matter of lack of confidence in my skills - I just don't feel sure I can pull off introducing the required curves in the full assembly all in one shot... 10 or 11 pieces, 8(9) aligned one way (the core), sandwiched between 2 more aligned perpendicular to the core.

I'm beginning to favor cheating for this task.

Though part of the point of this project was a deliberate exercise in patience, I'd rather NOT let all this effort pan out as a painful learning experience.