thanks for the update Jim. I'm drooling over your yard area!!
The rostratas look like they are getting established and growing nicely.
What are the wider leaved Yuccas?
Do you want to do a mass planting of Yucca filamentosa x elata seeds? I have plenty of extra Y. filamentosa x elata 'Big Mama' F2 seeds from last summer. I'm sure there will be some variation between the seedlings and it's always interesting to see how the F2 generation changes the characteristics.