Weekend mail call:Mike from Oakland wants to know if Joe Looney can handle the right guard position in the regular season if Alex Boone's holdout lasts that long.Bill Williamson: I think it gets to the point where Boone is out in September. I think Jonathan Martin -- who is the sixth offensive lineman -- could get a look as guard. Martin hasn't played guard in the NFL, but the 49ers could use him there. Looney has had success on a limited basis, but expecting him to play at the level of Boone may be a stretch.