I think I mentioned, this summer, on French Ebay, I bought a pair of old Lefol fenders for the Trek. Old Lefol fenders almost invariably come with tons of holes drilled in them, and generally the more holes there are, the cheaper they come. I think this pair was 25 EUR including shipping to my friend in Germany. I counted at least 10 superfluous holes drilled in them. Seems about right.
gugie has put bumper stickers over them. This is a good idea. Quick and affordable. But I really wanted to know if I could weld them. It was a burning question for me. I finally got the chance to use a really nice TIG welder that can do AC with high-frequency arc stabilization. This allowed me to answer my burning question.
So I tried it out. I prepped the fenders using a stainless wire brush and clamped some copper sheet to the back of the fender to cover the hole. I used 70% "cleaning" (electrode positive) bias. 60A max on the foot pedal. I used 1/32" 4043 filler rod. Pretty standard procedure, I thought. I messed up a lot and contaminated a lot of tungsten (the arc changes color and you get black schmutz everywhere when you do this) and finally developed/aped the technique in which I rested the ceramic cup of the tig torch on the fender and made a steady arc, which I pulsed using the foot pedal to alternately get more filler rod melted in (low amps) and get penetration on the hole's edges (high amps). By "walking the cup" (moving the tig torch's ceramic cup by degrees) around the hole, I could get to all sides.
There were 9 holes to fill in this rear fender. It took me about 2 hours to do it all. The welds are a little bit more brittle than the rest of the fender, but they could be cold-worked, by peening or crimping, to a certain degree. Here are the results. Six holes in the bottom photo and three and a half in the top photo.
There were two holes in the front that I did not want. I did these last, so they are the best of all.

You can see I was even able to preserve the hammered pattern a little. I am proud of this!
Was it worth it? Probably not if all I got was a pair of beat-up-looking fenders. Should just cough up the money to buy new Honjos, and save myself the time and effort. I'll still have to buy some Berthoud mounting stays for these, after all! But I learned a lot of difficult welding technique, and that makes it worth it.