Had many older style sliders that slid in a poured concrete groove. Most miserable things ever. Dirt and moisture gets in concrete groove and makes doors hard to slide or freezes them completely shut in ice and snow. Keeps them form blowing but that's about it.

Had some newer sliders made with bottom track that slides over rail on bottom when opened. Outside apron and floor are same level poured below frost level. Sank a pipe in concrete and made this receiver style unit for bottom track to slide over. No bump pushing things in the barn everything is smooth and level. Pour some antifreeze in the receiver pipe and no issues with freezing.

Pics are in this previous thread may need to do something different since your not cementing inside. I just don't like having some support that should not be driven over.

http://talk.newagtalk.com/forums/thread-view.asp?tid=23642