I wouldn't do it on a bet! This is one product that MFJ should not offer.
The wiring for most accessory sockets is #16, and it is bundled with a bunch of other wire before it gets to the fuse panel. Thus, it is very easy to overheat the wiring, even when current levels are below the sockets rated load (120 watts give or take).
While it is easy to dismiss the facts with rhetoric (it works for me, etc.), the fact remains that the most costly repair on any vehicle is an electrical fire. If you choose this route, you're on your own.