What is the best way to mount bass shakers in a couch and love seat? Can I mount them directly to the frame or should I run a brace across the bottom and mount them to that?

Thanks

I had mine mounted directly to the frame of the couch and love seat they were on. I checked every month or so to insure they hadn't loosened up on me and they were snug from the day I installed until the day I removed them. I have seen some installs that used an additional bracket as you mentioned, but I doubt that it adds/subtracts from the performance.

I have always mounted mine directly the frame. This setup has always served me well.