PatG,
The first thing my Husqvarna Viking Dealer told me was that Wal-Mart Needles weren't to be used with the Designer I USB & I should use Schmetz. After using 80s to hem Denim I kept breaking needles, went back in & she told me to use 90s or 100s for Denim. They are now carrying Organ Needles that work well too, and are a better value. FMQing is a delicate maneuver, & if one entity is off even a tad, it creates problems. I keep an array of Needle sizes, as I have a Small Home Sewing Business & never know what customers will bring me.
Google fabric type to find out the size needle you need for different fabrics, then try the next size needle when FMQing.
You mention that your Dealer carries 100 needles for $50, but what brand are they? Hope this helps.