witter we fitted for many years and the really thing toyota wise.....
Also with the right supplier and the product it will fit.,....
i have seen in the past bars from some suppliers that have been made but not to spec holes not quite in line etc etc this just adds hours of fitting and frustration to the job.
Bumpers most come off and many need to be cut to fit over the bar or some part of it,.,,
I would get the pros to fit it (unless you really want to fit it)and all is guranteed then when you tow should anything become a problem...
PS make sure you get the bar retorqued after the first run of towing (not many people know or get this done) yes they do come loose after time also
Also make sure the tow ball is suitable and of correct size for what you are towing....ball and pin or std ball just make sure the ball size is the same as your trailer or caravan etc ,.....
May appear expensive to have a dealer or specialist company do it eg witter dealer or lexus but in the long term for piece of mind and quality of products have it done this way better than an issue while towing.