If you are not on social security, and therefore don't have to worry about IRMAA --
When you are subject to the 10-year liquidation rule for newly inherited Traditional IRAs,
to spread the tax impact most evenly over the ten years,
your divisor should be : 10 - N where N is the number of entire anniversary years gone by.
In other words, with four years gone by, you want to take out one sixth of the IRA in the fifth anniversary year.
If you are a young beneficiary, or even not so young, this rule would generate much larger RMD than the RMD based on Pub590B formulas.
At a very high age, the Pub590B formula can overtake this calculation and require a larger RMD.
If the IRA is huge enough, there's nothing you can do about IRMAA.
