Not an FG XR6T...
I think what we'll all find, is that Ford put the speed restriction on the Falcon as weight goes up, not because it's dangerous, more so to stop the gearbox ass ploding.
At 110KM/H, it likes to try and sit in 4th gear, on boost when climbing a hill. when things start to get a bit steep and you keep the foot in to keep it climbing... You can just tell the gearbox doesn't like it, but back it down to 80km/h, it'll slip back to 3rd gear, and it's happy as larry.
I had an R33 GTSt on the back of my FG last weekend, it towed it fine, bar the weight going up hill, and chewing over half a tank of premium to get from Dulwich Hill to Wollongong. (Far too much fuel IMO!) It would probably cost me $90 in premium to go to Wakefield, and then another $90 to come home again.
I actually had to stand on the anchors and she did pull up. (ABS got a work out, but she pulled up in a hurry, I was quite impressed actually at how well it pulled up)