Yes! I highly recommend them.
And, being a steel plate, the force is spread across a much wider area and with a little BLUE LockTite on the surface too, there will be pretty much zero chance of the "cold flow" that aluminum will do under extreme pressure - causing loosening. (Otherwise, the C-beam holes get wallowed out as the aluminum beam shifts around under stress.)
And, as mentioned, beam plates (from Bill) capture the nuts so you don't need to get a wrench (or fat hands, in my case) up in there with a wrench to hold the nuts.
The plates make removal and re-installation afriggin BREEZE!
Worth every penny, IMO.
