Well, it fits - sorta. Main prob is it leaves too much of a gap between the plate part that prevents the hinge pin from coming out and the hinge pin itself. This gap is about 2x as much as the stock arrangement has. I'm sure you could epoxy a piece of scrap across the back to reduce the gap which would eliminate the gap. But there's still a prob -

On my 4.6SS, there is a protruding boss on the side of the bulk that matches a recess on the inside of these bumper support arms - that boss is not there on the Flux bulk (screw hols are there though) and in my opinion, this makes this weaker than the stock setup. HPI is supposed to be coming out with some improvements for the Flux, maybe this will be addressed. A pr of pics showing this part installed (HPI P/N 85060 - its in my 4.6SS manual on pg 52) - 2nd pic shows gap a little better. I'm staying with the zip ties for now.