Before I fry something, I want to slave my LSS to a Reissue 65 Twin. There's no effects loop on the Fender, so I was going to set the slave low, max the mid on the Fender, go into the input. No blow up problems?
I slave my Road King to my Deluxe all the time, I just put it in the instrument input and keep the slave volume pretty low to where when I turn the amp volume up to about 3 I can hear it fine.
There's no real load going out of the slave so it won't harm your other amp. I'd go in the left side of the twin (non vibrato/reverb side).