I'm aware of the fact that they share the same letter...
The J-25 introduced the dive flaps, leading edge landing light, and the boosted ailerons. Our J is a J-15 I think? And such it has none of those features. The L in real life, and in game, has the dive flaps, leading edge landing light, and boosted ailerons.
So my question is would a J-25 skin go on our J, the model that shares the letter, or on the L, the model that shares the same features.