I decided to try turning my own lens back to front (18-200mm zoom) but my camera wouldn't allow me to take photographs without the lens connected (there goes my pinhole idea). So, I borrowed my cousin's 50mm and stuck it in front of my own lens at 18mm - here is what I got (this has not been altered - the circle is how the image was produced).
I then tried it again with my lens at 200mm and found that it was too hard to focus. It seemed that I couldn't get close enough to the subject with this lens and the slightest movement was caught at this focal length - here is the result (this is one of the stamen at the base of the bell-shaped flower).
You can still see the vignetting at 200mm but it's not as bad as with the wide angle. I will try a range of focal lengths and techniques on my next experiment of this type of macro shot.
