Turn radii

Hi all, complete newbie here. I am receiving some base boards tomorrow to get me started and it is my plan to run Southern Electric 3rd rail trains, sorry but that`s my thing. I don`t have a great deal of space but I would like to have a continuous run two track circuit as the main feature. My question is, assuming Peco flexi track, what is the absolute minimum radius you can get from this track? Any advice appreciated.