@davesails7: checking the symmetry of the bridle is also rather easy. just tie the four attatchment points where flying lines are attatched to the mixer together with a line and tie them to some fixed object. then walk to the canopy and grab one attatchmentpoint wher the bridle meets the canopy and its counterpart on the other side of the kite. pull and compare. if they are different, just pull on the shorter one to stretch it.
@Johhnn: usually frontstalls happen if the aoa is too less when you depower the kite. so making B shorter usually helps. backstall usually is a sign that Zs are too long (or B and C too short). if your kite is rather well used i would recommend restretching all lines before retrimming. set your kite up like i described above and pull with a certain force (10 kg?) at each point. don't forget to check if both sides are equal.