RKII - Mute the direct sound in a Three-way setup

[MadisonV44]

I use the RKII in a Three-way setup :
- Direct sound to a 4x12 Mesa Cab
- Slave out for the wet sound (to a GForce --> VHT 2:90:2 --> 2x 2x12 Mesa Cab.)

Perfect to mix Wet & Dry sound and keep the direct power touch 8) . But in some cases I would like to avoid the direct sound to be heard and have the wet sound only.
I wanted to do so with the speaker output features. It would give me the possibilitie to send my wet sound via the slave and send the direct sound to ... nowhere (in fact to the B speaker - where is connected the dummy shorting cable)

I didn't tried it yet because I don't want to damage the transfo with a no load scenario ... and I don't know if the shorting dummy plug protect effectivelly the RKII of supercharge in that case. Is it safe ? :? :?: If yes the restriction is that I have to dedicate a channel for this purpose ...

An alternative setup would be to use a big resistance with no speaker and a switch directly installed between my Speaker cable and the 4x12 to mute the beast !! It would be available for each channel and more flexible ...

Any ideas & points of views ?
Someone using 3Way setups ?
Thanks in advance guys !