Heh, I remember this! In the end I used method A, but with the visor behind the "lip". To fit it in front would have needed really precise bending skills, wheras anything up to 1cm can be fixed with filler if it's behind.
The original reason I had this problem was because the JFO helmet model I used didn't differentiate between the visor and the "lip", so I cut it all off, not realising there was meant to be a vertical part to attach it on. I re-printed the visor, cut the edges away then glued and fibreglassed it onto the helmet. You can see the before/after images here:
Hot glue made a really strong bond between the acrylic and the fibreglass. After that I just masked it off and filled the gaps with isopon P38!