So my simple first advise is to adjust the length of the Z bridle until you are happy. It will often need to be lengthened.
My second advise is to adjust the depower limit or amount B fully extends past A on the mixer so it is correct for the factory kite. This is usually 25-27cm for a flysurfer.
Those advises cover most problems.
You can stretch bridles and you can also adjust bridles. Adjusting them offers a more permanent solution and the possibility to fine tune or alter the wing more. Generally if you change bridles at the kite to be more or less Cambered or Increase/decrease depower, you will get the effect of that locally and somewhat more from the kite overall. You can also get an effect to alter the arc of a kite. For example shortening the A bridles in the middle of a kite will make it not only higher camber and more depowered there and therefore the kite overall more like that but will also flattening it. If you were to shorten the A bridles at the tips, you would in addition to the other effects get a more C shape, which because the other bridles are still flatter would flatten when powered and be more C shape depowered. That is one method to produce PA change amongst others.
If you would like to make adjustments to all the bridles on your kite so they are more close to factory. You can use a method I call the Full Mixer Test, which measures off the shortest bridle and you then take those and calculate changes against a line plan. With flysurfer kites you can use things called LCL loops to make adjustments or add pigtails. Kites without LCLs are at a severe disadvantage trying this, and infact you would probably have to add LCLs to make adjustments. I think it is worth while considering not buying a kite that doesn't use LCLs and would be extremely hesitant to buy a used kite like that. It could take you many hours to add lcls. There is however restretching which works very well but needs repeating.