A good rule of thumb: if something was easy, always make it sound like it was at least a little hard. If it was a little hard, make it sound like it was impossible.

So! Taking a look at the first section of cylinders, while you definitely did struggle in the alignment of your ellipses to that central minor axis line throughout the set, I can see that you did improve in terms of getting it closer to correct more frequently, and perhaps more importantly, I can see that you were very attentive when it comes to actually identifying the correct minor axis. Whether it was off by just a little, or off by a lot, you were very conscientious and patient in determining that correct alignment and marking it out. That level of care in your analysis is one important half in terms of growth and improvement.

Of course, the other half is taking the time to take the trends and patterns into which your results fall into consideration and deciding how you need to change and adjust your approach to yield better results. You certainly did this and it shows, but there's still a ways to go - and I can't help but eye that declaration that "this wasn't as strenuous as I thought it would be" with suspicion. Of course, I know better - there's nothing else in your work that suggests a lack of care or patience, so I'm sure you put your all into this. Just a good reason never to admit that sort of thing!

Alignment aside, one thing I noticed is that you appear to have a good sense for the relationship between the two ways in which our ellipses shift, when moving from the end closer to the viewer to the end farther away. Both of these shifts - that is the shift in overall scale (where the far end becomes smaller than the closer end) and the shift in degree (where the far end becomes proportionally wider) - are aspects of foreshortening. There are cases when foreshortening is very dramatic (usually suggesting a longer cylinder), and both shifts are more extreme, and there are cases where foreshorteninig is much shallower (suggesting a shorter cylinder) and both shifts are more minimal in nature. What you demonstrated in your work is an innate understanding that you wouldn't end up with a strong scale shift and a minimal degree shift, or vice versa, as this would be inconsistent, suggesting both dramatic and shallow foreshortening simultaneously.

That said, looking at some of these - such as 135 and 131, I did notice a similar kind of contradiction, and you may have noticed that they felt a bit off, even if you weren't sure why. If we look at 135, we'll see that the degree of the ellipses are both somewhat wide, suggesting that the cylinder is definitely not moving across our field of view - there's at least a significant portion of it that is moving back through the depth of space, away from the viewer. Then, looking at the distance between the two ellipses (the length of the cylinder on the page), there's a fair bit of space between them.

If the degree of the ellipses suggest that they're in large part facing the viewer, then in order to still have that much visible distance between them on the page, it suggests that we're looking at a pretty lengthy cylinder. Were it on the shorter end, those two ellipses would probably be close enough to be overlapping one another. So that leads us to one last thing - if we look at the degree and scale shifts for this cylinder, they're all telling us that the cylinder is indeed relatively short. And so we still have a contradiction - some signs point to a longer cylinder, others point to a shorter one.

This are all important things to keep in mind when dealing with perspective, and 3D space. The viewer is given tell-tale signs that help describe that third dimension, the dimension of depth, and how these forms exist within it. Because it doesn't actually exist, we are free to contradict it at whim - but in doing so, we sacrifice the illusion we're working hard to produce.

Now, I've rambled a while about that, so I'll quickly address your boxes in cylinders. This exercise is actually more about the boxes than the cylinders - it teaches us to develop a more instinctual capacity to construct boxes that are proportionally square - that is, having a pair of opposite faces that are square instead of simply rectangular, so they can actually contain a proper cylinder within it. We develop this skill by taking the principle of extending lines from the box challenge (where we extend the lines of the boxes we've drawn, then see how far off we were from having them converge consistently, and using that information to learn and improve for the next set). In this case, we add a few more lines from the cylinders themselves, which would only align with the box's own vanishing points if the ellipses actually represent circles in 3D space. If they don't, then they must be ellipses and therefore squashed - suggesting that the containing planes would not be squares. The closer those lines are to aligning with the vanishing point, the closer the ellipses are to being circles, and the closer the planes are to being squares.

Long story short, I think you've largely done a good job with this, and most of your cylinders/boxes towards the end tend to get closer to being properly circular/square. One thing I did notice however was that you entirely stopped drawing through your ellipses (something we talked about being important all the way back in lesson 1), and because of this you appeared to be struggling quite a bit in getting those ellipses to actually fit properly within the planes. This would have certainly hindered your progress, and so make sure you take greater care with that in the future to make this exercise more effective.

All in all your work is looking good, so I'll go ahead and mark this challenge as complete.