control room/recording room in one

hi, as i researched for like a year on building an acoustically more proper listening environment, i'm finally at the stage of starting it.. now the to be built control room is about 12' by 14' (3,20 by 4,10 meters) and the vocal room is about 6' by 4,5' (2 by 1,5 meters) i know a vocal room that size is not recommended but since i don't have another option i'm just gonna try to get the best out of it so in this thread that's out of speculation.. for instruments (drums, guitar, bass, precussion, violin) i want to use the control room to record in, now my question is: what compromises do i need to make when it comes to studio construction in such a space? i couldn't find any info on this so any help would be appreciated i'm using the typical small room construction from john sayers as main reference with a 5x5' (1,5x1,5 meters) diffusor on the backwall, do i need to consider treatments other than this (ofcourse bass trapping and broadband absorption included) or will it work out quite properly?

Check out this thread http://johnlsayers.com/phpBB2/viewtopic.php?t=6916 it could be similar to yours. cheers john

unfortunately the studio i'm building is half that, but i think i can work with such a design as an extra reference thanks