I agree, I think.
What profile are you going for? I'm assuming a reflex or R/D? You have PLENTY of lemonwood for most designs once you add a bamboo back.
I don't know much about lemonwood itself, but 3/8"-7/16" has been PLENTY of thickness for any wood I have used in a R/D. (osage, black locust, ipe, massaranduba, coyote, brazilwood, goncalo alves, jatoba, bamboo, etc.) Maybe ERC, yew, or plum would want more?
Go with what ya got, add the ipe powerlam, and some reverse wedges toward the tips if you are afraid of running out of wood out there.
Good luck.