Your best bet would be to mock something up and then go to a place like Logan Steel, by some tube and then have them put a bend in it for a few $$$. It would be much cheaper then buying a bender, and much stronger/easier then a series of welds. Check out Rogers new Jeep, he has some modified fenders that are re-enforced with steel tube. The key with the flairs is to mount them with zip ties. Strong enough to hold them on for street use, but when you hit a tree/rock they will rip off with little to no damage to the steel. Carry a few zip ties and you can pop them back on before you hit the street again.
Also do a search for a company called Jeep Tubes in WA. They make some tube fender kits that just require welding. Not a bad price, but shipping would be expensive. They might give you some ideas though.