in-game block limit is changed by having cheats on (type sv_cheats 1 in console in case you don't know this

).
Then go into console and type sf_team_block_limit 50 (or how ever many you want etc), if you are on about making it the server default then you need to edit the .cfg file in the dedicated server folder, to which you need ftp access (or if its hosted on your pc just navigate to the sf folder in the dedicated server folder), i forget which .cfg stores the block limit, but just open them up in notepad and look through till you see the sf_team_block_limit.
Gd luck.
Forgot to mention if you have mani admin installed, just use ma_rcon isntead of putting the cheats on, so type ma_rcon sf_team_block_limit 50 etc.