Yes, the stab in full down and elevator full up give a massive pressure on the jackscrew.
There is also a video at avherald.com 'Video of manual trimming from full nose down to normal trim setting (Video: AVH):'
https://www.youtube.com/watch?v=hPi-_blIT50
The FO attemt it 1 minute and give up.
The position of captain is a little bit better and he need 30 seconds to crank 5deg up.
After that test, he was tired.
Now, MCAS can set up to 2.5deg per comand.
In case of ET302, the MCAS has allready turned 4.5deg.
So, the captain must crank 1 minute under heavy load, with much power.
In the meantime, he should also hold the airplain in a good attitude.
I think its impossible together with the extremly stressed and overloaded situation.
PS: the 'roller coaster maneuver' implied to relax the control column.
I think thats a mental stress too for the crew to relax it if the airplain has allready nose down and diving at 1000 AGL.
The logic of every pilot in that situation is 'hold the column back as far as you can! don't relax it!'
Thats a big conflict in your mind.