I did this on my Zizzo Liberte to try to get a little more reach. You can see it here: https://bikingtoplay.blogspot.com/20...-tall-guy.html

I didn't measure how much the curved stem gave me. I'm guessing it's in the 40-50mm range. About the same as the extension links, which I also applied.

The only concern I have--and it might be a big one for many people--is that the curved stem riser + links made the package too big to fit inside the fold (like the original Zizzo parts did). They fold to the outside, which makes the whole package significantly wider.