Technically to be a nerd about it, yep, if somebody pulls a pissy fit about it, it needs a cert if an inspector deems your drilling holes then fitting the crush tube is strengthening or weakening a structural member of the car.
That said, I had one on my EP82 and nobody noticed (and it was welded re-enforcement plates too).
Yup, they do benefit from the rear bar. Sit a heck of a lot flatter in corners, and the turn in improves a whole bunch.