Swapping them end-for-end isn't going to change the spacing. Also, both wing panels are identical in spacing, just mirrored.

Compare both LE and TE pieces with one another and confirm that the spacing is equal. Check that the provided sheeting and ailerons will extend far enough to fit if you build the wings as-is. If both are true and the spars are long enough I wouldn't worry too much, just build them as they fit. One of the many things that can happen to paper plans is shrinking or expanding due to temperature and humidity. I admit that 1/2" in the space of one wing panel is more than you would normally expect, but still within the realm of possibility.