Well most of my outdoor layout was planned, or should that be "unplanned" around Peco, not Piko, with some nice gentle curves and also some quite severe approx. R1 bends, I can hardly use the graceful word "curve" to describe it. The instrument used for bending the track, although I see this is hardly what you are asking, was the standard R1 belly, as has been mentioned. As for straights, yes it will lie straight but you have to accept that if your layout is anything like mine you will get subsidence etc in which case my experience has been to let the track float as much as possible, keeping the screwing or pinning down to a minimum, and then you may well get slight lateral movement, but this is just a matter of aligning the track as and when required. My constant advice is to try to keep the rail joins staggered, especially on the bends. Why didn't you lot tell me that before? I like Peco track but I have to admit I have not used anyone else's flexi track.