Jumping right in with your cylinders around arbitrary minor axes, while the set as a whole is well done, I'm especially pleased with just how confidently your ellipses tend to be executed. As a whole, you're demonstrating a great deal of control over your linework, without giving way to wobbling. That's always great to see. In addition to this, you're doing a great job of varying your rates of foreshortening, and are quite mindful and fastidious in checking the true minor axis alignment for each ellipse, catching both the more obvious and dramatic discrepancies, as well as those subtler ones that can be easy to miss when careless, and can cause us to plateau in our development - so it's always good to see that you're doing everything necessary to avoid that, and to continue your growth with this exercise into the future.

Continuing 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 applying the line extensions as carefully as you have, you've armed yourself with ample information to analyze your work, and make judgments on how to experiment with adjustments from page to page. While it's expected that there will still be plenty of room for improvement on this front, as there always is, what you've done here has definitely armed you with a good capacity to estimate your proportions, and that should serve you very well into Lesson 6.

I'll go ahead and mark this challenge as complete.