Nikz is referring to the butterfly friction leaf spring that sits under the LIGA chronograph seconds wheel. I think I actually left it in, but I can’t remember. The advantage of leaving it in is that you will add damping to the movement of the chronograph seconds hand — reducing judder. However, the downside is that the movement needs to overcome the friction added by this spring, so you’ll see a drop in amplitude when you engage the chronograph as a result if energy being dissipated as the damping spring slides. If your movement has healthy amplitude then this isn’t an issue.
Regarding the jewel setting for the LIGA wheel — I’ve done the replacement on a second Daytona and I found that the jewel hole in the dd movement was too small. So you might need to replace that jewel. Be sure to test fit the wheel before you try to screw the chronograph bridge down.
As I’ve mentioned elsewhere I do t use the chrono on the watch I did this swap on very much. My go to Daytona these days is my BTF meteorite dial Daytona on an oysterflex. I use the chrono often on that watch to time my runs, but when I’m doing so I’m not looking at the seconds hand so I don’t know if the stock dd chrono seconds wheel causes much judder.
