Starting with your cylinders around arbitrary minor axes, you've done a great job. You've been mindful of drawing your ellipses with confidence, so as to achieve smooth, consistent shapes, you've been very attentive to checking the alignment of those ellipses after the fact (catching both notable issues and the subtler ones that can easily go unnoticed, leading to plateauing of one's growth), and you've included a great variety of rates of foreshortening.

One of the reasons I ask for variety in this regard is to be able to see whether a student is picking up more intuitively on the relationships between the different manifestations of foreshortening - that is, the shift in scale between ellipses where the far end gets smaller overall due to the convergence of the side edges, and the shift in degree where the far end gets proportionally wider than the end closer to the viewer. Both of these are effectively visual cues that allow the viewer to understand that, beyond the physical length of the cylinder they can see on the page, there may be more length that occurs in the unseen dimension of depth.

The important piece here is that those two "shifts" need to operate in tandem. This isn't something I share explicitly in the material, simply because I want to give students the opportunity to discover this themselves (whether subconsciously or consciously). Then regardless of whether they picked up on it, and how deeply, I explain it here to solidify that element.

From what I can see in your work here, it seems you do understand it quite well, at least on a subconscious, intuitive level;. We can see this in cases like 143, where we see really dramatic convergence of those side edges, resulting in a very small far end, which is correspondingly very wide and circular. Nice work!

Continuing onto your cylinders in boxes, you've similarly done a good job. 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 your line extensions consistently and thoroughly throughout the set, you've been able to identify where your proportional estimations are off, and have been able to adjust them from page to page to bring your approach more in line with yielding more consistent results. There is certainly room for further improvement on this front, as is expected - one area you'll want to keep an eye on is the tendency to have your sets of lines converge in pairs, with those on either extreme of the form having their own vanishing points rather than both sides all converging to the same shared VP. This is a fairly normal issue and tends to be exacerbated as the cylinders/boxes get longer, creating more separation between those sides - so it's just something to keep an eye on.

All things considered however, you should be well equipped to continue forwards. I'll go ahead and mark this challenge as complete.