Back to ovals I see
The roll could still use some work. Right now, it's more like it rolls onto its other point, then moves itself again, rather than being carried by some momentum. You could have also shown a little more force in it initially tossing itself into the first roll, to show the power needed to make it back up onto the other point.
As the the diving board, awesome! Great weight, great emphasis, I really like the mid-air hang (gotta build that anticipation!) and the slight pause as the board bends down. The following quick 2-3 frames of squiggles to represent it flying off the screen are also well done to show the speed the oval has flown away at, whereas in your previous animation with the bouncing ball, the ball stays on the ground a lot more.
In the previous animation, you had the mid-air emphasis right, but you spent too many frames with the ball touching the ground and shifting in momentum. It makes the resulting bounce back up feel like it should be much, much higher, since it takes a significant amount of force to squish a solid object, and that force is then transferred back. If you want a good example of how balls react to impact, watch some videos of tennis balls bouncing and being hit in slow motion. If it doesn't have much force, it won't deform much. If it has a lot of force being applied to it (speed, getting hit by a racket, etc.), it will flatten and stretch.