I have been taught the armbar only by 3purples and 1 near black belt and 1 Japanese Jujitsu black. The near black or brown bjj person mentionedsomething which I have so far not heard elsewhere nor seen on the internet. Basically, when you dothe mounted armbar, it may be better to lean to the side, more so the better as long as the hold is not compromised. The theory is that, even in the normal bridge, you have to lift up your body, that, is, enerygy or effort is used to lift up your body, not to mention his arm. However, when you are doing it from the side, you are only going against inertia and the friction against the floor. And as those who know physics, friction for many surfaces is only a fraction of weight. I wonder why this philosophy is not more common and wonder about the drawbacks.