When I tried this, the foil tape caught the wind
Exactly!
This is great idea, to use something readily available, like alum. foil (every household has it), to locate and "memorize" original LNBF's position.
Unfortunately, as Bongu noticed, it does not work in windy environment.
I tried to improve it, by increasing the number of layers of aluminum, and adding cardboard core.
What I got, was still flabby.
Finally, went back to old "jig" (described earlier on this forum).
Another thing, the foil would not allow to access the rectangular bar for marking and drilling holes for LNBF holder, as it covers the bar's end.
Annotated pictures follow:
