We did a trial row of Napoli this year, they were one of our highest yielding carrots, we are waiting to see how well they store. The taste was okay, but not nearly as sweet as our main carrot variety, Nelson. We also grew another new variety for late storage. It is a Bolero hybrid called Naval, Bolero being an incredible storage variety, right up until the following July with little shrink. However, Bolero has an "off" flavour which has prevented it from being very popular as a commercial variety. We are hoping that Naval has the storage abilities of Bolero with better taste.
Many carrot varieties will get that size if you give them enough space and plenty of water. This year was a great year for carrots, lots of moisture in September which is when carrots bulk up and require lots of moisture.
Mads