Jumping in with the cylinders around arbitrary minor axes, I do have a thought as to why you might feel that things seem off. Currently it appears that the cylinders you've drawn fall into two main categories - there's cylinders with shallow foreshortening, where the far end is a little smaller and a little wider than the closer end, but only by a bit, and so the side edges converge very gradually towards a very distant vanishing point.

Then there's the cylinders like 150 and 148 on this page where the side edges appear to be kept intentionally more parallel. I do see this from students, where they attempt to force their vanishing points to "infinity" in the manner discussed back in Lesson 1, whether by misunderstanding or by actively trying to make the exercise less difficult. Unfortunately this circumstance is generally incorrect, by the simple basis that we do not directly dictate where our vanishing points should go.

What we control is how we wish for the form (or more accurately, the given set of parallel edges) are oriented in 3D space, and it is that which dictates where the vanishing point goes. The only circumstances in which the vanishing point would be at infinity is if the set of edges in question run perpendicular to the viewer's angle of sight - basically not slanting towards or away from the viewer through the depth of the scene.

Since our cylinders are freely rotated in this challenge, just as the boxes from the box challenge were, we can pretty much guarantee that none of them will be aligned so perfectly. So, it's important to ensure that all of our cylinders' side edges converge - whether gradually or rapidly. Furthermore, it is part of the assignment (as pictured here in bold) to include ample variety in the rates of foreshortening across the set.

Continuing onto your cylinders in boxes, early on I did see some cases where there was similarly forced-infinite convergence, but that didn't last long, and you've generally made progress throughout the set. 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 those line extensions correctly, you've been able to pick up on issues and address them, little by little, gradually improving your estimation of those proportions. That said, I do think that when it comes to the boxes themselves there is definitely room for improvement. Don't forget - just as with all the other exercises introduced throughout this course, the freely rotated boxes along with the line extensions should be included in your warmup pool. Improve on that front, and your cylinders in boxes will in turn become more useful.

I'll leave that to you to tackle on your own, and will go ahead and mark this challenge as complete.