Starting with your cylinders around arbitrary minor axes, there are a couple important points to raise here, but they pertain more to the underlying linework and how you're executing it, rather than the structure of the cylinders themselves. There are two main things that you appear to be less mindful of than you definitely should be:

• First and foremost is the use of the ghosting method. It is not entirely uncommon for students to slip in their adherence to the strict 3 step process (planning, preparation, execution) of the ghosting method, and you are definitely doing so here. As students progress through the course, they can be prone to getting a little sloppy in paying attention to the exact steps they're performing, and so the distinct 3 stages of the ghosting method can over time shift more and more of the responsibilities into the final phase (the execution), rather than separating them out as intended. Instead of ensuring that they're identifying the specific nature of the mark they wish to make and what the comfortable angle of approach would be in the planning phase, then getting familiar with the motion required to make that stroke by ghosting through it repeatedly in the preparation phase, and finally executing that prepared stroke with confidence and without any hesitation so as to maintain a consistent, smooth flow, such students end up trying to do everything at the same time, resulting in a more hesitant execution. Practice can diminish the impact of this (reducing the resulting wobbling and making it harder to catch for those who aren't attune to it), which can make it seem like this is entirely normal - but it's not. In this course, it's extremely important that you always push yourself to be aware of every action you take, and every choice you make. In being hyper-aware of those things here, we're actually rewiring the natural actions we take when drawing so that outside of the course you can focus not on how you're making the marks, but what it is you wish to draw, allowing your muscle memory and subconscious to handle the rest.

• In a similar manner, I noticed that you aren't consistently drawing through each of your ellipses two full times. You are drawing through them, but you frequently fall short of the 2 full turns of the shape, which again suggests that you're not being as mindful of the specific actions you're taking as you could be.

Ultimately the solution here is to reflect upon what exactly it is you're doing when you make your marks, and ensuring that when you freehand anything, that you're employing the ghosting method in its entirety, even though this will require you to invest more time into your work. And similarly, ensure that you are drawing through your freehanded ellipses two full times before lifting your pen.

One other smaller point, more related to the cylinder exercise itself, is to ensure that when you're identifying those minor axes in this exercise, that your line is cutting all the way through the ellipses. Leaving them shorter as we see here can make it a little harder to ensure that the alignment of your minor axes are correct, and there's really no reason not to extend it a little extra to ensure that this kind of error analysis is as useful and as clear as possible.

Continuing onto your cylinders in boxes, your work here is by and large done well, setting aside the kinds of issues I've already called out (although I do think your linework, primarily for your boxes, is better than in the previous section - this is a pattern I have actually seen before, where students will get sloppy for the first section, but when drawing the boxes they're less so, which may just suggest that at least for drawing boxes they've internalized the habit of ghosting their lines, but that it's still not as much of a conscious choice as it should be). 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.

Funnily enough, because you had a tendency to draw the red minor axis lines for the first section so short, I expected to see what is a common (though mild) mistake where students will keep their minor axis lines for this section quite short as well. I'm thrilled to see that this was not the case, and that you extended those lines just as far as the others, ensuring that you'd have the easiest time possible to compare those convergences, and identify where your approach could be adjusted accordingly. So, good work on that!

All in all, there are things for you to work on, but they will be better addressed through your regular warmups rather than by extending this challenge, which was otherwise done well. I'll go ahead and mark this challenge as complete.