I ran on to this some time ago and I have not done the weights and measurments on my own FJ but soon will.
I thought it best to share this with those of you that are pushing the envelope of your FJ and those of you that are not, just in case you might want to and do it with relative safety.
Knowledge is a great thing to have, no matter where it comes from.
I offer you this link to one of the best articles I have yet to read on the subject of Roll-Over.
Center of Gravity and Roll-Over Angle - Jeepaholics Anonymous
Enjoy and be safe, MoSun