ToshAuer said..
Have been pondering the idea of whether or not an old kite on a compatible bar and lines would be safer and perform better? Has anyone done this before?
Cheers
Tosh
Putting a late model bar on an older kite will not make it perform any different, the performance of the kite comes from its intrinsic design, the design built into the kite itself.
There may be some improvement to flag out safety, but if you don't know what you are doing you may make things much worse too. Get the set up you decide on checked out by someone who you know to be well experienced.
Like IanR said above, the old Flexi still felt like an old and less evolved design, and flying it on a modern 2014/13 bar would not change that.