Sorry, I don't quite understand. There's no way to attach endplates to a midwing--in most cars they are attached to those flip-ups inside the rear wheelsMIDWING
And on the BMW the midwings are much further forward, coming out from the middle of the engine cover over the middle of the sidepods (the 2 pictures on top are the relevant ones...you can see in the top right picture that there is no midwing toward the back of the car as it is with the Ferrari--the BMW midwing is further up)
Again, then, I don't understand. When these midwings are already attached to other pieces, how could they have endplates? Is it a different wing that you have in mind?