The 'drawings' are quite good at showing the possible/likely result of placement of these coils. It is obvious to me that the original manufacturer was more concerned about efficiency in manufacturing than the known results of such placement. That puts me in another camp, where simply remaking this crossover on a larger board would allow the distance needed to avoid these simple problems in the first place. A smallish circuit board is tempting in its own way to use, but then allows other problems to occur.