2.5 dry is really a great first year harvest or just 5 plants.
As an example I planted 8 rhizomes this year. 1 died. I had one that I thought had done extraordinarily well and only got 4-5 oz dried from it. One of my other plants I ended up with .5 oz dry. Other than that My other plants either had just a handful of cones or didn't produce any this year. I have heard planting crowns is better and gives you more of a second year yield... looks like it worked for you.