Using Degelman RR1500 Rock Rake to Windrow Rocks

Rocks are a problem here, as they are on most(?) farms. We've picked a lot by hand, used a skid steer, etc. but nothing has really worked for us given the limited time frame we have to get this kind of field work done. I bought the rake and a Riteway 900ST picker last year and so far, they have performed well.