I have been flying X-UAV Talon for 2 years on mapping projects, once I saw there was a possibility to include wing extensions so you would get more lift to carry more batteries an increase your flight time. However they were discontinue
Today I was flying my quadcopter with arducopter 3.1.2 and APM 2.6 with Ublox GPS, vibration levels where excellent between 0.4 and -0.4 on X and Y and 0.4 -0.4 around 9.8 on Z axis, alt hold and loitter where working perfectly, so I decided to