A plane is a plane. Lift, thrust, drag and lift. Lose your headwind component and you may be in for a world of hurt. An additive will ensure safe operations.
I can't recall what the manuals said in the light singles or twins that I have flown, but I do recall adding 'some' when it was windy and gusty. On the MD-83 we added either ½ of the head wind component or all the gust, which ever was greater, to a max of 20 knots. On the B767 we do the same, but combine the two.(again, max 20kts) Keep in mind, for those of you that are worried about over running the stopway, that with the additives your ground speed will be reduced by your headwind component. Thus, if your approach speed is 70kts, and you add 15 because the wind is 20 gusting 25, then your approach speed will be 85, but your ground speed will be 65. Once crossing the threshold, your additive for steady state wind is to be bled off and your correction for gusts maintained, so that your IAS will now be 75, and ground speed will be 55!!!
Any average pilot should be able to, without much effort, stop his a/c in a shorter distance on a nice gusty and breezy day in shorter distance than on a calm day. Perhaps on a light a/c your additive might be 5 or 10kts max, or something like that... I don't know. Play it safe. Don't try to be a hero. If the approach looks like it is going into the toilet, abandon the approach and try again.
Oh, and I hope my math was correct for the above now that I am looking back up at it. Please correct me if I am wrong.
Slopey... B767 company limit 33kts dry. MD 83 was 30 demonstrated. I think.. at least that. Did that with no problems. HS748 was 30, again if memory serves correct. Did that too, no problem... very nice handling plane. Worst wind I saw was in Churchill, about 30 or 40 degrees off the runway 49G60. Made for a very short landing. I'm not bragging here as I do believe that I am not an elite pilot of any sorts. Just been there and had to do that.
I hope this helps. Cheers.