Another poster here on bf had mentioned the lack of sun protection by the stock visor on his helmet. I had the same problem with the visor on my Giro helmet. As popular as recumbents are becoming you would think that Giro, Bell or some other manufacture would make a visor that works for a recumbent rider. This got me to thinking that I could probably solve the problem. I know there are some commercially available add on visors but I didn't like the looks of those I found. I wanted one that looked like it belongs on the helmet if not an original.
I set to work making a template out of cardboard (from the back of a writing pad). With a little work I was able to design a visor add on that could be fastened to the original visor but added better sun protection on the sides and front. Being satisfied with the template I used a sharpie marker to black it out and then used packing tape to make it a bit more resistant to moisture. Then using two sided mounting tape, I attached it to the original visor.
Below is the results:
After a couple of rides, I was quite happy with the results, and decided it was time to make one from plastic. I ordered a 1/16" thick, 12"x12" black ABS sheet from Amozon. I pulled the template back off of the helmet and proceeded to make the plastic version. I now have a helmet visor that will give me better shade from the sun, both in front as well as from the sides. The new visor adds 1 1/4" of material below the original.