Starting with your cylinders around arbitrary minor axes, you've done a pretty great job overall here, with one minor concern to keep in mind that I'll mention in a moment. As a whole, you're executing your marks with a lot of confidence and clear use of the ghosting method - resulting in smooth, even ellipses, and straight side edges. I'm also pleased to see that you're checking the alignment of your ellipses quite thoroughly, picking up on fairly small discrepancies. This is something that will help you avoid plateauing as you're getting into that region of "good enough", where it's easy to stall in one's growth if we're not super meticulous about identifying even minor mistakes.

The one area where I did want to offer some advice is in regards to the way in which the two shifts from one end to the other - that is, the shift in scale, where the farther ellipse gets smaller overall due to the convergence of the side edges squeezing it down, and the shift in degree where the farther ellipse gets proportionally wider - are to work in tandem with one another.

While I didn't notice any glaring mistakes, I did notice a tendency in some cases to have these two shifts operate somewhat independently of one another - that is, a tendency towards having the shift in scale occur a little more significantly, with a more tempered shift in degree. Honestly though, the extent of this was very minimal, and I expect this explanation to help solidify the concept for you going forwards.

Basically, these two shifts are both manifestations of foreshortening, and they tell the viewer just how much of the cylinder's physical, three dimensional length is visible on the page, versus how much of it exists in the "unseen" dimension of depth. When the two shifts fall outside of a general range of cohesion, the viewer can notice that something seems a little off, though they may not be certain as to why that is.

So, be sure to keep that in mind going forward.

Continuing onto your cylinders in boxes, I completely understand where you're coming from - but it really comes down to something I mention a couple times in the material, both in the video and the written material. 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.

I talk about how mistakes are expected to occur as part of the process, here:

What makes this so much trickier than the extension method for the boxes alone is that there's a lot that could be going wrong. First off, your minor axis alignment could be off. Secondly, you may not have drawn the ellipse to fit snugly within the box. Thirdly, the planes you drew your ellipses in may not really be squares in 3D space.

This error checking method serves to help us work on gradually building a more intuitive sense for the proportion of these forms. Don't get stressed if you're constantly turning up mistakes - it's entirely normal, especially with so many different factors to control. The point is to gradually get better.

As a whole, I'm quite pleased with your progress here. You're employing the techniques provided for analyzing your results well, and while there are certainly still plenty of areas where your line extensions show room for improvement, you're very much headed in the right direction, and I can see your judgment for those proportions improving throughout. Just keep in mind - the ellipse is not the problem. It's all about the box.

That's not to say you don't have the odd outlier that deviates more significantly, like this one here, but whaat's important is that you identified the correct minor axis regardless, which showed just how far off this one case was. Mistakes will happen, but as long as we identify them, we can learn from them.

So! All in all, good stuff. I'll go ahead and mark this challenge as complete.