In reading your post you may want to check two additional things.

1. Your planting dates. It's late almost everywhere in the country to be establishing a perennial. You don't want a dry-hot period to hit before the crop establishes a root system deep enough to access moisture. It may be to your advantage to wait until fall to seed.

2. Your fertilizer. From what I've read and heard about Extreme, it needs nitrogen and you mentioned none. What you added sounds more like a legume application. I think about 50 pounds of nitrogen per acre (Considering the plot size you may want to add 50 pounds of 34-0-0 before seeding) is called for with this crop at planting time and an additional 25 pounds of 34-0-0 after the plants are 4" tall. With the second application be sure the plants are dry.

This will be critical since you are late spring planting. You'll need fast establishment to get through the late summer and most perennials are slow to establish even with the correct fertilization.

I've talked with 3 guys who have it growing and they like it but their's was planted early and they added plenty of nitrogen.

Good luck.