Question: I'm eyeballing placing a randomwire that would cross over some
corrugated aluminium for a few feet. Not touch it, but within a foot or two.
What would this do to the antenna's characteristics?

Thechnically, the aluminum will affect it but for receiving, I wouldn't worry
about it. When I had no options, I never worried about a warp in my antenna
pattern when I used it for transmitting.

I imagine one of the technically active in this group can give you a better
answer.

The only good part of my antenna here is that it runs perpendicular to the high
voltage lines that cross the front and the rear of my 75 foot lot. (My metal
trailer is 65 foot long, barely enough to support the ends of my 40M inverted
vee.)

73,
Bill, K5BY