Looking over your work as a whole, it's clear that you've shown considerable improvement in a number of different areas. Over the first section, your control over your ellipses was certainly okay to start, but by the end the overall comfort and confidence with them had grown considerably. You also became more attentive to the 'true' orientation of your ellipses' minor axes, which in turn helped them improve more rapidly.

I also noticed that you intuitively seemed to maintain the correct relationship between the scale-shift (where the farther ellipse is smaller overall than the closer one) and the degree-shift (where the farther ellipse is proportionally wider than the closer one). Often students will just pick at random whether they want the far end to be smaller and if they want the far end to be wider, and by how much, but what they don't realize is that one basically forces the other. If the far end is much smaller, then it tells the viewer that the cylinder itself is longer. Similarly, if the far end is much wider, then it suggests the same thing - that the far end is a lot farther away, and that the cylinder is longer.

If however you have the far end being considerably smaller but roughly the same proportional width, then you end up with a contradiction. I haven't seen any of these contradictions in your work, which suggests that you at least intuitively, if not consciously, realize that this relationship needs to be maintained consistently in order to avoid cylinders that look "off".

Continuing onto your cylinders in boxes, I'm very pleased with the progress you've shown here as well. The key thing about this exercise is that it is primarily about the boxes, rather than about the cylinders. Specifically, it helps students develop a more intuitive grasp of how to construct boxes that feature two opposite faces that are square in proportion. We do this similarly to how the box challenge has those line extensions, which help us gradually get better and better at having our lines converge consistently. By adding the cylinder, and its own line extensions (from the contact points and minor axes), we are able to test whether or not the opposite faces containing the ellipses are actually square. This is because those additional lines will only align to the vanishing points of the box if the ellipses themselves represent circles in 3D space. If they do, then it's fair to assume that the plane containing them is square. And if they don't, then the student adjusts their approach as they go, bringing them closer and more in line.

On this front, you've demonstrated a good deal of progress and confidence. One thing however that I want you to keep an eye on is that when your boxes get longer, it can be rather easy to forget that we want the lines of both ends to converge at the same vanishing point. If you look at the top right box/cylinder of this page, you'll see that especially for the lines going straight up, they're converging in pairs instead of at a single shared vanishing point. It's an issue we see in the box challenge too, but it tends to come out more here because cylinders tend to lean more towards longer boxes.

Aside from that, you're doing quite well. I'll go ahead and mark this challenge as complete.