your welcome, your case interested me so i tested, and i made a mistake, it's not about the dynamic speculative, it's in the interpolate mode, basically you keep the rigidbody discrete, and the interpolate make a smooth lerp between two physics update, allowing you to lower the number of updates, of course it's not great looking if you look close but that's not important in your case, if you wonder, in my pc i managed to run more than 8000 cubes at the same time with a decent fps