I tried using natural watermelon flavor in a wheat last summer and found the juice was too fragile to reduce on the stove, even at very low temperatures. The end result tasted burnt and was unpalatable. So this year I went with artificial flavoring. Brewed 5 gal extract kit of the American Wheat, added 8oz of the flavoring post-fermentation, and then bottled it 4 days later. The end result was a very watermelon forward wheat beer. It tasted kind of like a jolly rancher. Some people loved it, others not so much. It is clear in color so it does not impact the color of the beer at all. In the future I would dial it back to 6oz or perhaps even 4oz to just give it a hint of watermelon. But the product did what it was supposed to, so I would highly recommend it if you want your beer to taste like watermelon!