I can basically test anything I can attach to the car and will fit inside the wind tunnel. End plates on F1 cars aren't really a regulation thing, it's more to prevent flow on the very edge of the wing (tip) from bleeding over the sides and creating turbulence. The reason why planes have them like that is that you want to minimize the bleed while also minimizing surface area. Minimizing the bleed means minimizing loss of lift and reducing drag somewhat. Winglets or end plates don't inherently create downforce/lift, they only aid the accompanying airfoil in producing downforce/lift. I'm not an expert but I would imagine curving those fins in wouldn't do much of anything except maybe increase stability. Unless they were airfoils like on the Ferrari FXX
