I usually temper hickory,(with a heat gun), at floor tiller or brace height. I personally have trouble with hickory checking during the treating process,so I want to have enough wood to scrape during final tiller to remove the checks,so make sure you have a good deep treatment. Other whitewoods,such as the Elms or Hophornbeam,rarely check,so I may treat them again when I'm closer to final tiller. Tempering bellywood brings an amazing transformation to the stave in my opinion,just remember be careful not to scorch the wood,(it will break ),and, to give it 3 days to stabilize with the relative humidity.JMHO , God bless