I am trying to put a large (?) rocket into orbit, but I am still having problems which I believe are of aerodynamic nature. However, with the ever-changing model of aerodynamics in KSP (I'm using v1.7.0), much of the advice I read on this topic is either outdated or too simplified to be complete.
I have a four-stage rocket, with my payload consisting of the mobile processing lab an inline wheel and some scientific instruments in a bay.
I realize that a rocket like this is overpowered for a Mun outpost (as it's named), but for the sake of this question, please assume that I need this much δ-v for some other reason.
As I understand, the center of lift should be below the center of mass (gravity) and this is what I believe I achieved using wings.
I tried many other, but similar designs. For example, I enclosed the thinner part of my rocket and the landing struts into a fairing. I also tried to use more wings, larger ones (like delta wings), put elevons on them, and tried different placement configurations (only on the main thruster in the middle or the boosters on the side etc.)
Inevitably, the end result is the same. As soon as I reach a couple of kilometers and around 300 m/s of velocity, my rocket starts flipping over uncontrollably. With some designs, it is also spins around its z-axis, but I was able to reduce or eliminate that.
This happens both when I control the rocket myself and when I use MechJeb to launch it, so it cannot be due to my poor flying skills. The usual advice to "slap some fins on it" is also clearly not sufficient here. I also know that protrusions can negatively affect the flight performance of some rockets.
How can I successfully fly a rocket like this? Are there other factors apart from aerodynamics that contribute to my failure?