Best way to smooth fender bolts?

I have done this a couple of times and this is how I did it.
weld a flat washer to a cut off bolt, then tack the flat to underside of the fender lip. Then plug weld the hole that is left on the top of the lip.
Now remember that this WILL raise the fender up the thickness of the washer, and may or may not be an issue. However if it is you will have to modify the inner fender monting lip to accomodate the washer/bolt arangement to allow the fender to sit in the proper location. Sounds worse than it really is. Good luck and post some pics.