Belaying two followers with Mad Rock Mad Lock in Guide Mode

Can anyone comment on using the Mad Rock Mad Lock belay device. I am particularly interested in belaying two followers on two different ropes in guide mode. The Supertopo Review talks about how easy it is to pull slack through when belaying followers on two different 10mm ropes, but the directions on the packaging that came with the device say you should only belay one person at a time with the Mad Lock.

I am guessing that you just have to pay extra attention with the Mad Lock when belaying two followers at once. For example with the Reverso 4 you have to keep a brake hand on both ropes when the angle of the two ropes coming out of the device is very different, and you also have to take precautions on the second rope when the follower on the first rope has taken a fall and you have to "unlock" the first rope.