Starting with your cylinders around arbitrary minor axes, great work - you've done an excellent job of varying your rates of foreshortening, playing with different orientations, and have for the most part avoided the pitfall of eliminating the foreshortening altogether (we see it in a couple places like the big one on the middle of this page, but once or twice in a set of 150 is not really a concern).

I did notice a few places where the degree of the farther end should have been considerably wider (like the bottom left corner of this page), and this is somewhat more prevalent throughout your set, suggesting that it's not a once-in-a-blue-moon hiccup. It's either a lack of conscious awareness of the need to make that far end wider, or perhaps an issue in actually controlling how wide your ellipses come out - in the sense that you may be aware of what you need to strive for, but your arm may simply not be agreeing with you. If it's the former, that's definitely something you'll want to reflect upon, as the concept of the degree shift is discussed in a variety of places throughout the course (the ellipses section in Lesson 1, the organic forms with contour lines in lesson 2, as well as in the cylinder challenge itself). If it's the latter, then you may want to make a point of including more ellipse exercises in your warmups. The funnels and organic forms with contour ellipses exercises do a good job of focusing on this, as does general use of this same cylinders-around-arbitrary-minor-axes exercise.

Carrying onto the cylinders in boxes, you've generally done a good job here, although I would advise you to give yourself a great deal more time for each individual mark to ensure that you're applying the ghosting method correctly, and giving yourself ample time to plan and prepare for each stroke. While I'm pleased to see that the execution of your marks here (both ellipses and straight lines) are confident, they do give the impression that they perhaps weren't each as planned out as they could have been.

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.

Overall you've done a solid job of this, applying your line extensions consistently and correctly throughout. There is one point to keep an eye on however - make sure that when you're drawing your ellipses, you're striving to have them touch all four edges of the given plane. Looking at your work there's a good chance that you are striving for this - ultimately everything is subject to our current skill level, and so controlling those ellipses with that specificity does require practice. As long as your intent is to have those ellipses touch all 4 edges however, then you're good - you'll get better at it, and as you do, those line extensions will become more valuable and your estimation of those planes' proportions will similarly improve. I'm mainly noting this here just in case it wasn't something you were as attentive to, so it can be addressed as you practice this exercise in your warmups.

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