This never happened to me. Like somebody else said, you may be landing with too much vertical velocity. YES, drag is really bad in KSP. Why don't you use FAR ? I think it is a good thing that the drag is like this for now. Yes, it is less realist, and yes, your rockets need more deltav to get to orbit. But your rockets are also easier to fly. It's a good thing you can learn how to fly with this bad drag model, and then, when you master it, you can install FAR to get a better drag model. Not sure it is as easy as you think. There WAS a good reason. Your design must be bad. I guess the problem is that when you burn a certain amount of fuel, your center of mass gets behind your center of lift. At least, that was the problem with my spinning planes. Well, not sure of it, i am clearly not good with planes (never landed a plane !). Are you serious ? use a more lightweight engine on your upper stage. As there is less weight, a less powerfull engine should be OK. The mainsail is just a piece of crap, except for massive first stages (where it is the only viable solution). It's only quality is it's high thrust, it does not have a good ISP. On a bi-coupler ? Yes, sure. Like the mainsail only makes sense when you want high thrust and don't care about ISP. Or the nuclear engine for the exact opposite. That's fine like it. Every engine has it's utility for different situations. Standard pieces, economy, realism. Same answer for custom-size fuel tanks. This would be really unrealistic and would really change the game in a cheaty way. Sometimes you fail to land because your rocket is too tall and you still have a little horizontal velocity... With your suggestion, this would not happen. Too easy !