I read somewhere that watermelon should be back sweetened or used with another fruit. I think both could not hurt. Either way you should read what you can about it, and then experiment for yourself. The best writers in the world can't tell you how it tasted in such a way that you taste the exact same thing. This is why I like taking notes when I make a wine, especially a new recipe. By the time it's ready to drink I want to make sure I have an account of what I did so I know how to adjust the recipe for the future.
I think the Strawberry Watermelon is definitely one to make again in the future, but it is a little on the dry side. I'm considering adding in some rhubarb to balance the additional back sweetening that I would do next time around. There is definitely a pronounced watermelon flavor, but it I think there is so much sugar in watermelon that there is not much left when fermentation is over. Maybe more strawberry too. Looking back I see that my starting gravity was 1.090; maybe I need to aim a little higher and let the remaining sugars stay in the wine.
Overall I would say this is a good wine, but I think it could be better with more sugar from some source. I definitely plan on making it again and letting it sit longer before bottling. There is a lot of pulp left over from the watermelon that is now collecting in the bottom of the wine bottles. The lighting in my kitichen threw the coloring off a little, but you see what it looks like here:
It's actually a pink color, but the kitchen lighting gives it a different shade.