When I finally got a helmet last year, it created a new issue for me. My old (Oakley) goggles were fine in the down position, but whenever I would put them up on the front of the helmet, they would fall off. They would either slide back and end up dangling off the back of my helmet, or they would slide forward crashing into my eyes unexpectedly and with a lot of pain. I bought these Giro goggles, because according to the marketing propaganda that came with my helmet, "Giro goggles are designed specifically for their helmets". I fully thought that this was just marketing speak, but since I wanted new goggles anyway, I thought that I would try these out. They really do work. Because of an adhesive band on the inside of the helmet strap, the problem I was having is completely gone. These goggles stay in place as well on the front of the helmet as they do on my eyes. Problem solved.
Aside from solving my eye smacking issue, these are all around great goggles. Good fog resistance, clarity, visibility, and protection. They do everything that I want goggles to do, just as well or better than my Oakleys which cost three times as much (albeit 14 years ago) do.
I highly recommend that you try these goggles, especially for use with the Giro helmets.