For the first endomorph the timing is the same.
The second endomorph however, has a little less time than before, since it should mix with our new third endomorph.
To accentuate the stretching effect, we set tension 1 for the maximum point of this new endomorph (100%), giving it some anticipation to what will happen later
The trick here is to position the bounce drop, exactly in the same place in the which is our third endomorph (100%) so that the forms fits perfectly; and I say to position (although it has been modeled in the correct position) because so that the effect is perceived in a flowing way, we should animate this drop from down (from the position where was the drop that falls), toward up (until the exact position where it fits with our endomorph). The same as with the endomorph, we should set tension 1 for the drop motion (Y axis); although the drop animation from down to up will never be seen, (the drop should be dissolved 100% until before our endomorph is in 100%), is important to animate it this way because it will provide us continuity and fluidity in the dynamics of the effect.
Barely appears the drop separated from the tank (dissolve 0%), our third endomorph passes from 100% to 0% in only one frame, being replaced by the fourth endomorph from 0% to 100% in a single frame.
To know in a simpler way, which it should be the timing for the fourth morph's disappearance, is advisable to animate the third endomorph in a continuous way, from the moment that it appears (0%) until it arrives to its maximum point (100%) and then smoothly disappears again (0%); after taking note of the number of frames to obtain the correct timing, we can set its disappearance like the step 12, and to apply the same timing for the fourth endomorph.
The drop should continue descending more slowly than the fourth endomorph's disappearance
When finally the drop passes through the water tank, we dissolve it from 0% to 100% in a single frame
The result should be more or less this.
The animation can be downloaded here.
Besides this, I've played in a composition software with the image tonalities, filmgrain, brightness and contrast, etc.
I wanted to thank to Julez4001, thanks to his generosity is possible this tut. And to all those that offered help, thank you!