My experience with solar panels has been that they are very sensitive to partial shading. The panel elements are in series so partially shading one can drastically cut the current for the whole array. Even minor shade from branches or cables can have a significant effect. On my install I mounted the panel between the Beef Bars so it is not shaded by them. You might want to put an ammeter in line with your panel and experiment to see how much of a hit you’re taking. Cheers.