I have not had the same luck with the fog city insert. In the rain, it would still fog up after about 10 minutes of riding. I did install it into a brand new visor, but it did not stick very well and would start to work loose when it got wet. Then it would fog between the insert and the visor (which you can't wipe clean without removing the insert, tricky while riding).
If you have not installed a fog city insert, the adhesive is on the perimeter (maybe 4mm wide), so trimming to shape can be trickier, if you are trying to adjust for the nose of the Arai XD.