Nice wind break Mark, but be aware that Leylandii Cypress only last about 25 years or so and get very leggy if not pruned annually!
The last big storm we had here on Central Coast with gusts of up to 71 miles a hour from South east blew over many tree's!!! Big Eucalyptus and many Leylandii Cypress!!! Neighbor in front of me has been cutting down all his L. Cypress he's afraid of them falling on house.I've watched the Leylandii Cypress for 25 yrs. plus around my property neighbors on side and both property's in front of me were surrounded in them by developer who built houses on those property's. I've been on my place for last 40yrs. and watching them all come down slowly but surely!