Why keep the factory JJ's in there any more? I had recently bought a new JVM410H to correct the mistake I made in selling my first one a couple years ago. I yanked the matched quad of =C= before I sold it, and had another in stock. Now that I'm sure this new head is stable, I popped in a matched quad and am wondering why I waited. Not a bad project for a day where it's -5F outside.