I guess you could put an image point on each of the top corners and spawn at:
x = lerp(player.imagepointx(1),player.imagepointx(2),random(1))
y = lerp(player.imagepointy(1),player.imagepointy(2),random(1))
offcourse you should choose the random number between 0 and 1 before using it inside the expression,
that way the position will be on the line between the points..