I like to thin the top plate until it measures a certain deflection when loaded with a standard weight.

This old plane is the standard weight

underneath the supports is a dial indicator to measure the deflection

a better veiw of the dial indicator

I also measure the thickness of the plate with another dial indicator

Cutting rosette channels in the top with a dremmel router.

Lyndsay's guitar will have an exotic wood (imbuya)  inlayed into the top with bands of veneer on either side

Wood ring liberated from the its block