Aluminum skin floating on the bottom edge

[DesertApprentice]

I have read many posts and watched videos. I'm still not clear whether I should cut off 3/4" from bottom of alum skin.

If I don't cut the bottom of the skin, the trim screws will go through the alum, it will be pinned to the ply. Will this cause problem because the alum is not "floating"?
If I cut 3/4" from the bottom of the alum, then the alum bottom will only be clamped by the trim, therefore it's "floating". But cutting always scares me, once done, you can't uncut it

My hunch is either way is OK. It appears people are doing it both ways. Any advice is appreciated.

Thank you!

 

[Tony Latham]

I'm still not clear whether I should cut off 3/4" from bottom of alum skin.

The sheathing needs to cover the surface. (all the way to the bottom)

Tony

 

[Greg M-TNT]

If you’re worried about movement, you can bring the aluminum skin all the way down, mark where the screws for the trim will go through the skin and then drill the skin with oversized holes before final install.