Mike Wolfe at Mesa Boogie support told me that on a Dual rectifer when you pull a set of power tubes and 1 rectifier tube, you then need to run your cabinet in the next lower ohm jack. So, if you were running your cab/speakers at 16 ohms, you now run them in the 8 ohm jack..... 8 ohm speakers would now be ran out of the 4 ohm jack.
I think that's the same thing you're asking? That was straight from the mouth of Mike Wolfe at Boogie.