Jumping right into the cylinders around arbitrary minor axes, at first glance, your work here is done very well - but upon closer inspection, I noticed with a bit of horror that for the first 90 cylinders, you appeared to apply the error analysis of the ellipses' minor axes incorrectly - focusing not on the ellipses individually (and marking one red minor axis line for each) but on the cylinder as a whole, which unfortunately would not be able to account for the potential discrepancy between the different ellipses, and thus force you to lean more towards one ellipse or the other.

Given that your cylinders are generally very well drawn - with confident linework, smooth ellipses (which on occasion you forgot to draw through two full times before lifting your pen) - I was very relieved to see that you caught this mistake and corrected it for the last 50 cylinders. Where the mistake would generally have had me assign some revisions to ensure that you do understand how to apply the error analysis step correctly, you preempted me on that so it will no longer be necessary. Just be sure to go through the instructions more carefully from the beginning to avoid this in the future.

Continuing onto your cylinders in boxes, despite your concerns (which I will address in a moment, as I do have a suggestion that may help), you did largely perform this exercise well. 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.

The only issue I noticed in your execution was that you were only identifying the individual minor axes, as opposed to extending them as far back as the other lines - so you may have confused the instructions for this step with those for the previous section. Here we want to be able to easily and quickly glean useful information at a glance, so ensuring the minor axis lines are extended back all the way will help us better compare the extensions and identify notable issues in their convergences.

I did however have a thought come to mind from how you talked about the various different points of difficulty of the exercise - getting a smooth, evenly shaped ellipse, touching all four edges of the enclosing plane, and aligning to the desired minor axis orientation - that may help with the issue. There are indeed a number of separate problems and your observation is not inaccurate - when you've got so many things to juggle, every step becomes difficult.

What can help is creating a hierarchy of priorities, so that you're not constantly worried about all three in equal measure, which can make it harder to gain ground and actually improve in a direction, out of fear that it'll impact the other aspects negatively. Given the principles of markmaking from Lesson 1, we do already have our first priority - executing our marks with confidence, so as to achieve smooth strokes and evenly shaped ellipses. This is more important than touching all four edges, and more important than getting the alignment right, because the less evenly shaped the ellipse is, the less accurately its line extensions (the minor axis and the contact point lines) describe the plane itself. Not to say it always has to be perfect - we can use a stiffer ellipse to better understand what the proper ellipse would have looked like, but it definitely makes things harder if we sacrifice that confidence in favour of, say, being able to force it to touch all four edges.

When you're comfortable executing those ellipses confidently, the next priority down would be the minor axis alignment - for the simple reason that where the contact points give us 4 things to worry about, alignment technically gives us just one more additional concern. Being off in this alignment by a little in either direction is of course entirely normal - but the closer it gets, the less we have to worry about what adjustments we'd have to make to get the minor axis to fit (along with the contact point lines), the fewer major variables we have to concern ourselves when deciding how to adjust our box proportions going forward.

And third, the contact points themselves, getting them to touch the side edges. This is, out of the whole list, the least important both because those contact point lines and their alignment is already determined by the box itself - we're just discovering it, so we can test whether they were correct, or whether they were off (and by how much). In cases where you end up missing the edge, it's actually fairly easy to see where the ellipse would have touched the side edge, so we can still generally get that contact point more easily. We still want to get as close to touching that edge as possible, but just as how a stiff ellipse can be used to better understand what the evenly shaped, confident, smooth ellipse would have been, here even in missing the edges it can still help us envision what the "correct" ellipse would have looked like, and where it would have touched those edges.

Hopefully that will help - but from what I'm seeing, you're applying the instructions for the exercise well (just be sure to extend the minor axis lines further), and are arming yourself with the information you require to continue honing your ability to estimate those box proportions.

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