In theory it might have been a good idea but the result is terrible. But let's first recap how coupled mode works. In coupled mode you specify your desired velocity vector (strafe input depending on current ship orientation multiplied by speed limit (maximum ship speed when speed limit is disabled)). The IFCS in coupled mode determines how to use your thrusters to achieve the new velocity vector in regards to your current velocity vector. In other words the IFCS determines the energy (thrust power * burn time) each thruster has to perform to achieve the new velocity vector. Pre 3.10 the IFCS would use the maximum thrust power of each thruster resulting in different burn times for each thruster. In 3.10 the IFCS now determines the minimum burn time needed for each relevant thruster and then uses that burn time for all thrusters, meaning that only one thruster uses maximum thrust and the others use only so much thrust that they get their job done right at the same time as the one using maximum thrust. This results in a constant acceleration until the new velocity vector is achieved whereas before the acceleration would change each time a thruster has reached its needed burn time. This has nice some effects: For instance when letting go of your strafe input (new desired velocity vector 0) the current flight direction is maintained (TVI stays in the same spot) until you come to a full stop. It might also be beneficial for aiming and hitting enemy ships and providing a more stable platform for your turret gunners (but this obviously goes the other way too, you are easier to hit because your flight path is slightly more predictable). Additionally this mode is better suited for precise landing/docking. In theory this sounds good, but in practice this is really bad and getting the most out of your thrusters is very counter-intuitive. Let's make a simple experiment (keyboard input in the example, but it's the same for all input devices): I'll use the Avenger Titan. The main thruster of the avenger can produce a maximum acceleration of 8.4. The side thrusters can produce 3.4. Now in coupled mode (G-Safe off) with SCM speed limit enabled strafe left (A-key) until you reach the SCM speed limit. At the same time let go of A and press W. Now look at you G-meter: You get 4.9. which is a lot less than the 8.4. That's because the IFCS cripples your main thrusters so it will have the same burn time as your side thruster needs to counter the drift. It will still take the same amount of time until the desired velocity vector is reached as before 3.10, but now in that time you will have traveled far less in the forward direction. This alone is pretty bad, but it gets worse: Start the same: In coupled mode (G-Safe off) with SCM speed limit enabled strafe left (A-key) until you reach the SCM speed limit. At the same time let go of A, press W and disable the speed limit. Now look at you G-meter: You get 8.6. At least that's more than the 8.4 of the main thruster alone, but you will notice that it will now take a lot longer before the sideways drift is eliminated. To be exact the sideways drift is eliminated at the same time the speed limit of the ship is reached. That's because the IFCS now does not use the full side thrust to counter the drift. To get the most out of your thrusters you would have to constantly adjust the speed limit or use the exact analogue strafe input in a very counter-intuitive fashion. In that specific case: instead of disabling the speed limit, you would need to set the speed limit to SCM * 8.4 / 3.4, so that it would take the main thruster at maximum thrust the same amount of time to reach the forward speed as it would take the side thruster to counter the drift). This of course was a very specific test, but you will have the same problem for nearly all combinations of current velocity vector and desired velocity vector. This results in a very bad flight experience in coupled mode, because you are almost never using the maximum potential of your thrusters. You will not accelerate as fast and drift a lot more. This is especially apparent when trying racing in 3.10. In coupled mode without a speed limit enabled you will drift a whole lot more than necessary and with a speed limit enabled you will not use your main thruster efficiently. Even when doing lots of oversteering it's almost impossible to maximize your thruster output. Constantly adjusting your speed limit or using analogue strafe input is probably the best way to race in coupled mode in 3.10. But it's nearly impossible to maximize thruster output this way (especially because it's very counter-intuitive). My guess the only way to race efficiently in 3.10 is using decoupled mode. But to reiterate, it's not just a problem for racing. It's also bad for dogfighting especially when there are obstacles (asteroids/debris) you have to maneuver around. I really think this "vector stability" change to the IFCS in coupled mode results in a very bad flight experience in these situations. I racked my brains trying to think of a way to combine the benefits of this mode while still maintaining maximum thruster output, but it's just mathematically impossible for ships with multiple, differently powerful thrusters. CIG should revert this specific change or at least add an option to switch between these modes, although I don't really know why anyone would prefer the new mode for racing or dogfighting. As both modes have pros and cons my preferred solution would be to provide the pilot with an ingame toggle to switch between a "max thrust" coupled mode (3.9) and a "stable" coupled mode (3.10) depending on the situation. (Edit: made some tweaks to clarify that the new "stable" coupled mode is not all bad) Edit2: I've come up with a way to implement a coupled mode that has vector stability while still being great for racing and dogfighting. See here: https://robertsspaceindustries.com/spectrum/community/SC/forum/4/thread/proposal-anti-drift-stable-coupled-mode-including-/221300 If the coupled mode would work like that, there would not be a need to have multiple coupled modes.