Chomp,
What are you connecting to that curved track is probably the important question. If the curve is continuing, you may want to solder another piece of flextrack to this one on your workbench, and then lay the much longer piece down on your layout, because soldered flextrack on curves is easier to lay down in a smooth radius.
If your next piece of track is a straight piece, you will need to trim or nip off the end of the curved track so that the ends of the track are even. This is so you can use rail joiners to join the curve to the straight.
You really don't want to be sliding the rail in the flextrack any more than to ensure that one end of one piece of track is snug to the next piece of track, if you get my meaning.
Northern_blues