I'd start with wheel spacers in the rear and go from there... the rear wheels look too inset to start with at the OEM offset - adding spacers would help balance the look. Fender flares only accentuate the problem and only make sense if you're running wheels too wide for the stock arches. Fender flares are a form WITH a function.
Edit:
After looking a bit more, nice 6ULs... Guess I needed the coffee this morning lol. Are you at the limit of what the stock fender flares will support? Still seems like overkill unless you're trying to run wider wheels/tires, but if you've got a reason for them and it solves the problem, go for it.