Andy, RE the helicopter, you might like this tutorial I recently;t posted on choosing the right perspective convey scale.
The perspective you chose, horizon line above the object and vanishing points far away from the center of the page, tells me that this is a small object. A larger object is going to have the horizon line much lower and the vanishing points closer together. Would you be cool with me doing an overlay of the design in a perspective that conveys the size? I’d love to use it as the basis for one of my “Tutorial Tuesday” videos. I would of course give you full credit for the original design.