I'm going to assume that they're in (mostly) chronological order, since past the first few pages you stopped providing any kind of useful numbering. In the future, remember that numbers are really helpful both in pointing to specific instances when discussing particular issues and in just being able to tell the order in which these were completed. Conversely, noting the number of cylinders on the page isn't particularly useful.

Now, that aside, your actual work throughout this challenge is quite well done. Starting with the cylinders around arbitrary minor axes, you've been very diligent in identifying the 'true' minor axes for each ellipse. One thing I did notice was that aside from a few cases, you did stick to a relatively limited range of foreshortening. One thing you might want to do in the future is to play with more variety in this regard, including both shallow foreshortening as well as very dramatic foreshortening (and everything in between).

One thing to keep in mind when getting into more dramatic foreshortening, where the vanishing point is closer to the object, is that not only is the far ellipse going to be considerably smaller than the end closer to the viewer, but the shift in its degree from one end to the other will also be more extreme. So if we look at examples like the bottom right of this page, you'll notice that the shift in scale is quite extreme, but the shift in degree remains fairly limited, making it feel a little off. This is because both of these 'shifts' are visual cues that tell the viewer whether the cylinder is longer or shorter. In that one, looking at the shift in overall scale tells us that the far end is much further away, and therefore it's a longer cylinder, but looking at the shift in degree suggests the opposite.

Continuing onto the cylinders in boxes, I think you've largely done a grat job here, with my only complaint being that when drawing your ellipses inside of those box faces, it is critical that you draw them confidently to keep them evenly shaped, rather than deforming them to fit the space. This is something we tackle back in the ellipses in planes exercise, so be mindful of that.

Other than that, this has come along quite well. This exercise primarily focuses on training the student to better judge proportions in 3D space - specifically having them learn how to intuitively create boxes that have two opposite faces which are roughly square. We achieve this similarly to how the box challenge uses line extensions to train students to keep their lines parallel in 3D space (by having them converge more consistently towards a vanishing point). By adding ellipses/cylinders into the mix, we add three additional lines for each ellipse - lines which will only converge towards the box's own vanishing points when the ellipse in question represents a circle in 3D space that rests along the surface of the box.

As we repeatedly go through this process, then do the line extensions to check our results, we identify where those alignments are off, and where we can make adjustments. Then we try again, make those adjustments, and repeat the process. As we do this over and over, we train our instincts to better judge the relationships between the things we draw on the page, and the proportions/relationships we're aiming for.

Looking at your work, you do appear to have gotten considerably better at constructing boxes that are roughly square in proportion. While I do feel the unevenness of some of your ellipses may have hindered this a little, it did not present in all cases, and you had enough analysis/information on which to continue pushing your growth throughout the set.

All in all, your work here is coming along well. I'll go ahead and mark this challenge as complete.