Really to many governing factor's for a strat answer
main reason I see people do it is to elimanate wheel scrubing which tells me that there 4bys not set up correctly eg to bigger wheels for susspension travel bla bla
me personaly done it to my 4by with a 2'' susspension lift and 30mm tray lift
and a 2'' body lift . At that had no wheel scrubing loaded or not (flat tray way over GVM loaded) . I done it to stop it leaning so much when loaded eg back wheels still traveled to much under tray on the side of a hill and was a lot more prone to roll over and was just scarry
I done a 75mm reinforced box section extention lightly welded to the rear diff housing works a treat and tuff as nail now can go along the side of a hill with 1000/1200KG on it angels of 20/25% no worries

still got to be carefull
very top heavy loaded up
nearly rolled over in a customers driveway one day had to get the missus
to open the passangers door and hang of it was at the point a coke can rolling a cross the floor would have changed the out come :shock: new I had to think of less wheel travel then scarred the poo out of us front passangers wheel would have had 1.5/2 m of day light under it came up and just sat there for a little then slowly started to move towards the shiney side down
the missus's 65KG and the weight of the door open was the saving factor here
But thats why I done it so like I said at the start to many variants
do it if you need to .......don't do it if you don't
would not have done this if it was'nt built for carrying over 1000kg on it's back theres no point empty it's fine all ways was