IMO Bosh spends at least half of his time at C. Whenever Nesterovic is not in the game Bosh is the center. According to 82 Games.com the second most utilized 5 man unit for the raptors last year included Bosh at Center. He also played center in 4 of the top 10 units:

http://www.82games.com/0607/06TOR15B.HTM

Rotoworld lists Bosh as a F/C:

http://www.rotoworld.com/content/pla...=930&sport=NBA

As does Yahoo:

http://sports.yahoo.com/nba/players/3707

And ESPN:

http://sports.espn.go.com/nba/player...?playerId=1977

The two other players in Toronto's big man rotation are Bargnani and Garbajosa. Both are listed on the player pages as F only:

http://www.nba.com/playerfile/andrea...ani/index.html

http://www.nba.com/playerfile/jorge_...osa/index.html

Bargnani's game is definetly not that of a center although he is tall. And Garbajosa has been mentioned as a possible starter at SF.

http://www.nba.com/fantasy/fantasy_p...orge_garbajosa