Removing Power Tubes in a Rectifier Head to lower its wattage:
The power tubes in most MESA amplifiers work together in a push-pull configuration and in matched pairs. With a few exceptions (like the Road King) they are matched in a mirrored arrangement. Looking at the power tubes from the rear of the amp the two outer tubes are matched to one another and the two inner tubes are matched to one another (the 2nd and 5th tubes are also matched to one another in the case of a Triple Rec). It is okay to remove one of these pairs of tubes to reduce the wattage and headroom in a non-Multi-Watt version of the Dual or Triple Rectifier. It really won’t matter which pair you pull as long as you pull two tubes that are matched to one another. The Multi-Watt Dual and Triple Rec have a built in 50 Watt power setting for each channel, so there is no need to remove tubes in these models.
If you use the Rectifier Tube setting on your amp go ahead and pull one Rectifier Tube (it won’t matter which one).
If you run an 8 ohm load on your amp, you’ll likely find your cabinet(s) now sound better plugged into your 4 ohm speaker output or that a 16 ohm load sounds best plugged into the 8 ohm output.