I did the same thing at the rear as the front, I like the 2x3 tube method better then the plate meathod. If your floor pan isn't super clean and rust free then the 6x6 plate would probably punch right through it if you put your car on it's lid. I also agree with what was said abouve about putting the a pilar bars through the dash, mine are in front and they are a P.I.T.A. to get in and out of the car. I'm changing that since I'm 25.5'ing my car. here is a pic of the rear on my junk.
Steve