buy aluminum, a little more costly but you won't have
to cut the legs/feet. aluminum will have an adjustable
angle.
also purchase an attic tent to install in the attic
over the stair case if your access is within your
living space. this will stop attic air and temps
from entering your living space. pull down attic stairs are
very leaky, and leak more as time goes on. also
it will also add to insulation value at this area.

best of luck