I bought a Precision bass body in ash, and I'm fitting an Allparts neck with Fender pick-ups. The problem is, when I fit the scratchplate the rear pick-up ends up sloping down towards the neck and although I've tried packing foam etc under it to support it, it still keeps happening. It has to remain free to float on the springs. I've tried it over and over again, and the pick-up keeps on sloping at the front. Any ideas?