The S550 IRS Subframe alone/bare bones, weighs 55lbs. Just thought I would share that. As for the IRS in general, our 2010 Camaro has cut MANY low 1.3, high 1.2 sixties. We did recently break a halfshaft. We discovered it was one of the early GForce units....and was not rated much above 800HP. We have been making 900+ftlbs for 3 years. lol!!! Rest assured, we now have the Outlaw Shafts from Gforce. On that note, I do have some GForce/FRPP Halfshafts on the way for my 15. I was more than excited when GForce told me they were building their baddest of bad halfshafts for the FRPP pieces. Those shafts are withstanding 1500HP, and have never seen a failure. That is astounding.