Nice work overall! Starting with your cylinders around arbitrary minor axes, you've done a great job in executing your lines and ellipses with confidence, achieving smooth, straight strokes, and even shapes. You've also incorporated a lot of variety in terms of the orientation and foreshortening across the set, which shows quite clearly that - whether consciously or subconsciously - you understand how the degree shift from one end to the other gets more or less dramatic as the scale shift from one end to the other itself gets more or less dramatic. This is something I keep an eye out for, as I find that students retain something they've discovered themselves more strongly, than if they're simply told ahead of time - but it shows that at least at an instinctual level, you're understanding how the marks you draw correspond to a realistic depiction of 3D space.

I'm also pleased to see that you're very fastidious in checking the alignment of your ellipses, catching even fairly small discrepancies, which ultimately helps you to avoid the everpresent risk of plateauing as you get into the "close enough" territory.

Moving onto your cylinders in boxes, your work here is similarly well done. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

In checking all of your line extensions thoroughly here, you've helped give yourself ample information in the analysis phase, allowing you to gauge how your approach should be adjusted from page to page, in order to bring those proportion estimations back together. Over the course of the set, you've definitely improved in your sense for those proportions, regardless of how the box itself is oriented in space. I expect this will serve you well into the next lesson.

I have just one suggestion - with many of your boxes you tend to have one dimension in which the edges of the box remain fairly parallel on the page. This isn't inherently wrong (although it would be if, in cases like this, all the sets of lines are drawn as being parallel on the page), but it does imply something you may not be intending.

There's only one limited set of circumstances in which a set of lines on the page, representing a set of edges in 3D space, would have their vanishing point at "infinity" (resulting in them never actually converging). That occurs when the set of edges are running perpendicularly to the viewer's angle of sight in 3D space. In other words, where they're not slanting towards or away from the viewer through the depth of the scene, just running straight across their field of vision. If it is not your intention for the form to be aligned in that fashion, be sure to include a bit of convergence, even if it's only very slight.

So, that about covers it! I'll go ahead and mark this challenge as complete.