by the time you try to blend all 4 corners of the car, both fenders and quarters, you just paint the whole car..... Yeah ummm not a DIYHmm, I would certainly consider cutting and drilling my fenders a "customization". The whole point of these add-on flares was that it would be an inexpensive way to add fender flares for the look (not the function) without modifying or replacing any existing parts - in a "DIY" way. Once you start talking about cutting and drilling fenders (or replacing fenders), it's no longer an inexpensive mod for the DIY'er.
I can only imagine the cost involved to replace the fenders, paint them, etc. Just not worth it at that point.
We're not talking about a small difference in price between the two methods...