A bit late, but I hope this reply helps.
You can connect setrack fishplates to flexible track if you carefully snip off the curled lip with fine snips, being careful not to crush the end of the fishplate.
It is extremely easy to remove a setrack fishplate. Turn the track piece over. You will see a dimple where the fishplate has been mechanically pincered into the bottom of the rail. With a sharp 1.5mm metal drill in a hand-held chuck, sit it on the dimple and give it about 6 turns. You will shortly see the fishplate wobble slightly. Another five or six turns and you should be able to easily pull it off with pointed pliers.
(And yes, it's good enough to re-use!)
