About 10 g of elderflowers (dried) seems to do the trick for me. This amount produces a beer where the elderflower is noticeable. I suppose 5 g would be the minimum that could provide a noticeable elderflower kick in 40 pints following my method.
Method: Bring dried elderflower to the boil in water then turn of heat. Empty flowers and solution into primary FV. After a few days syphon to secondary leaving elderflowers behind. The first time I used elderflowers I didn't do this and they kept blocking by little bottler and getting into the bottles.
Of all the brews that I have done, the elderflower beers go down best with the not ale drinkers and chicks every time.
Method: Bring dried elderflower to the boil in water then turn of heat. Empty flowers and solution into primary FV. After a few days syphon to secondary leaving elderflowers behind. The first time I used elderflowers I didn't do this and they kept blocking by little bottler and getting into the bottles.
Of all the brews that I have done, the elderflower beers go down best with the not ale drinkers and chicks every time.