My Sire V7 five string has noticeably diminished output on the middle A string due to the bass's setup. I don't believe that I can "push" the pole pieces up without damaging the pickup, and I've heard of folks effectively extending the pole pieces by adding small neodymium disk magnets to their top. Who can talk to me about this? Does it change the tone? Do they stay put? What size are you using, and where do you get them (although there are plenty of dealers on eBay). Thanks in advance for your input.