Re: stock fenders / reinforcing ?
What helped my fenders the most was installing a small L-bracket on the center mount to help the original center mount cope with the added stress. It mounts on the same bolt as the center mount (and front brake, if you have wheel brakes) and if the original mount went forward on the fender, I just let it there and ran the L-bracket pointed toward the rear. I drilled the fender and put a small bolt with a lock washer on it. Then, the two brackets (original and the new one) get tightened up under the same bolt through the front forks.
That doesn't mean that you don't have to have solid mounts for the rest of the fender though. I run one on the front and the rear of each fender. Having two mounts on each fender, plus the center mount really stiffens them up.