Tagged/Pinned builds in RSS feed?

Is it possible to specify either a tag or pinned=1 in the RSS url?

Right now I have:
http://build_server/guestAuth/feed.html?buildTypeId=bt70&itemsType=builds&userKey=guest&buildStatus=successful

Which allows me to watch all successful builds only, but what I'd really like to do is further filter by either:
http://build_server/guestAuth/feed.html?buildTypeId=bt70&itemsType=builds&userKey=guest&buildStatus=successful&tag=mytag

or

http://build_server/guestAuth/feed.html?buildTypeId=bt70&itemsType=builds&userKey=guest&buildStatus=successful&pinned=1


Is this possible?

Thanks!