What you've got to remember Andrew is that you and I are talking from experience with laying flex. This might be going in the Academy for new hobbiest to learn from.
If you take 6 ties out of joint of flex and then bend to desired curve, it will kink and be out of gauge. Your looking at 1 3/4" ~ 2" of unsecured rail being bent. Sometimes just 1/2" makes a kink.
As for cutting the rail joiners down, dont cut them in half and expect them to work well. When soldering a full joiner, the only points being soldered is the outside edge of the rail, and even then 90% of connection is electrical with hardly any strength coming from the joint. We're not welding rail, just attatching tin/lead mixture to the outside of it.:thumb: