Mike was using these for drop tops, not acoustic backs.
You really want stable wood for backs and tops on acoustics, building in tension(unwanted tension) is a bad idea. If a top or back is mildly bending, you can heat it up and work it back to shape. If it is radically twisting it would take several sessions with a fair bit of heat to get the wood retrained and stable. Each time you heat wood it will lose a bit of strength (not bad if it is one or two sessions), but many with high heat and you may lose a lot of strength. So use good judgement when doing this for acoustics, and absolutely flex the wood at the end of the process and see if it is still going to perform as you want it to.
Peace,Rich
Thanks to Rich's help the walnut came out beautifully!