I just got the standard latest version {not Lynch} for a 71 Super Bass. This one has a bass cut or boost and high gain or lower gain. You can put 10 different pedals in front of the amp and the reaction with this is very different, plus this adds almost no extra noise. I use it with an attenuator and it really sounds great. Really tightens up the amp and adds just enough hair to have enough gain to be usable for rock tones. Throw a pedal in front and now you have enough gain for metal.
I was pretty skeptical about this, but its surprisingly good and no mods to the amp, which is the whole reason I bought it.
With the side set screw it does not move around, is tight in the socket and the clip, once clipped, is nice and tight. I would probably check it before a gig, but I doubt it would come off without some force, or a shitty grab to begin with. I Have already moved the amp around and brought it to a few different places with no issues. For this particular amp, and for $199, I am pretty happy with it.