hey everyone! I am a novice apm copter user coming from KK2.0. I have an rc explorer tricopter which I decided to convert to apm 2.6 piloted drone. However I struggle just to stabilize the copter. for some reason it tends to drift to the left. I tried swapping motors with no result, also made sure that the motors are mount true to the ground. arms are 10mm square cf rods with wooden dowels glued inside - very straight and strong, only 60g more weight totally than hollow cf. no drift issues with KK2...  props are gemfan 11x4.7 a little soft, but my AUW weight w/o FPV equipment and 2700mah 3s zippy flightmax is about 950g. my compass/gps are mounted on a 10cm mast away from any DC wires. also, I performed acceleration/compass calibration multiple times as well as synced ESCs (plush 30amp). 

with KK2.0 I used to take off from my garage and into the street around my house. with apm2.6 I cannot keep it within 4-5 feet in the horizontal plane of the spot I need it to be. 

I would happily provide more info about the build  if necessary, just do not know which is needed. 

Thank you! 

p.s. apm is in its case mounted on little pads of the Kyosho Zeal Gel Tape just in the corners of the case.