Yes,even Mechjeb was not able to keep it going steady..until I actually put the only engine on that stage to be a gimbaling one, and include RCS.. as for the Rocket, I\'m too lazy to boot up my gaming PC now, but it was a stock parts center stage with 5 Fuel Tanks and one LFE-30, surrounded by four four-fuel-tank stages with one LFE-45 each, fuel crossfeed from the outer to the inner tanks (so when I decoupled, the 5 tanks in the middle were still full) - as soon as I decoupled, the craft spiraled out of control.. I also tried a 3M Design including a Nosecap once, and that had even more spiraling issues because of no gimbaling engines at all in the design.. flying the beast felt like crazy. And even after I modified the design with a LFE-45 for the center stage too (so it can gimbal to compensante for tumbling) it was very hard to keep it steady.. and even after being left only with the skycrane system, it was extremely hard to fly straight. just for example, I tried launching with the skycrane only.. which should give me a solid nice upwards thrust motion, no? It did a backflip even before I fully cleared the launch tower.. Update: I just did a manual fly in orbit, and as soon as I powered up the engine, the craft spiraled out of control.. since this time I didn\'t compensate for it, it actually TORE OFF THE ENGINE due to shear forces.. pictures of the flight: First picture, launch with Mechjeb (tends to crash in the tower if I fly it manually) Second picture, directly after Stage Separation..so far so 'good', even though it is not very good on keeping the inclination I want.. Third picture, after Mechjeb 'gave up' (200km apo, -50km periapsis.. yeah..) I manually powered up the engine, and up to this point, was going in a straight line. 10 seconds later, I was wildly tumbling (the ship was doing about 10+ rpm at the time of the screenshot) and about 5 seconds later, the engine tore off.