You'll need to search for the fitting instructions on sites like Towsure and PF Jones, they seem to stock all the popular bars.
Most bumper cuts for bars aren't visible, they are usually underneath to allow an under and up fitment of the hook/ball/bracket.
I considered fitting my own bar and dedicated wiring kit to my Panda 4x4, so I rang my dealer to check about any warranty problems.
I was told there was no problem, even fitting a 7 way bypass, as long as it's fitted properly, to be sure they suggested some sort of proof a pro fitted it would be handy.
They put me in contact with their towbar man, he's a mobile fitter that covers a lot of dealers in the South of London, not just Fiat, though he turned up in a Doblo and knew all the Fiat products very well.
He fitted the lot, at the dealers for less than I could have done myself.
A nice tidy detatchable Thule with a flip up electric socket, you really can't tell there's a bar fitted once the hook and ball is removed.
All for £365.
