I would not recommend a tuck position for any of the drills... all layout flyaways. We stay away from the tuck as much as possible when having a fear issue such as this as the tuck becomes an instinctive fear position many times and causes more crashes. We spot all of the layouts until they are able to do them high enough to land without fear of hitting the bar. We stack blocks or use the spotting platform by the pit bar to put the coach about shoulder height with the bar (maybe a bit higher depending on the height of the flyaway). That way the coach can aggressively hold the gymnast off the bar if they pull in.
Once everything is fixed using a single layout flyaway... then we would move to high layouts to the back into loose foam or on a soft resi landing. Once they can do that... then we would move to the double tuck again (usually over loose foam so they can flip slow and soft). We would again be spotting the double like stated above so we can aggressively hold the athlete off the bar if something goes wrong.
Once we are back to normal... we would then continue to spot using the back slat method to keep the flyaway where it needs to be.
At any point... if even one flyaway pulls in (even a little bit)... they are required to go back and do some sort of single layout to prove that they can distance themselves from the bar properly.