Very nicely done! Starting with your cylinders around arbitrary minor axes, you're doing a great job of varying your rates of foreshortening, and checking the alignment of your ellipses quite fastidiously. I always encourage students to include lots of variety when it comes to the foreshortening, specifically to look for how much a student understands and incorporates consistent 'shifts' when moving from one ellipse to the other.

Basically foreshortening manifests in two ways. There's the obvious shift in overall scale, where the farther end is drawn smaller than the closer end, causing the side edges of a given cylinder to converge towards a shared vanishing point. Then there's the shift in degree, where the ellipse on the far end gets wider in proportion compared to the closer end (though this widening will happen on all forms, not just cylinders).

The key point to retain here is that these two shifts happen in tandem - either you get a more dramatic shift on both, or a slight shift on both, but you'll never end up with a situation where the shift in degree is more noticeable than the shift in scale, or vice versa. Otherwise that would result in a contradiction, where one thing tells the viewer that there is more foreshortening (and therefore more distance between the ends of the form) and the other suggests there is much less foreshortening.

For the most part, you did seem to keep those things consistent. There were a few little areas where I'd say there was a bit of contradiction, but it was quite minor. For example, on cylinder 122, there didn't appear to be a shift in degree, but there was some shift in scale.

Continuing onto your cylinders in boxes, you're doing a great job. Checking all of your line extensions and adjusting your approach based on that analysis is very clearly helping you further develop your intuitive grasp of how to construct a specific kind of box. That is, a box that features two opposite faces which are proportionally square. We achieve this by adding the line extensions for each ellipse - that is, studying the minor axis lines and the two contact point lines for each one. The closer these are to converging towards the box's own vanishing points, the closer the ellipse is to representing a circle in 3D space - and therefore the closer the plane that encloses it is to being proportionally square in 3D space.

I can see that your proportions have indeed improved over the set, and while there's of course still room for further growth, your improved intuition and instincts here should help you out throughout the last few lessons.

I'll go ahead and mark this challenge as complete. Keep up the good work.