Brock,
I've built two guitars w/ Koa tops, one a six string, the other a twelve. I really pondered how to handle this. The wood is--as you well know--quite a bit different from spruce. First, my pieces were heavier, say 25% heavier than a typical spruce top. Then to compound things, they weren't as stiff longitudinally as a good Sitka top. Hmmm. What to do?
The notes I made at the time stated that the wood, when tapped, had a deep fundamental, with lots of overtones as well, though not as "clear" as spruce. What I ended up doing was taking the top down to .115" in the center, and thinning the perimeter a good bit. For the bracing, I used the stiffest spruce I had, and braced conventionally (no real differences in size or placement of braces). Admittedly, there was more intuition here than science!
The sound? It was wonderful, surprisingly so. Sure enough, it didn't sound like a spruce guitar, but no one cared. It didn't have the shimmery highs, or the sparkle you might associate w/ spruce. It did sound "darker". But it was a sound the owner loved...and so did I.
I think you will enjoy the experience. Keep good records of what you do, and see how your piece of Koa stacks up against the spruce you normally use. You might want to discuss with the future owner what not to expect with a Koa topped guitar.
Hope this helps some,
Steve
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If I had it to do over I would gone with less curl