Starting with your cylinders around arbitrary minor axes, I noticed that you were quite diligent in drawing your ellipses with confidence, analyzing the true alignment of your ellipses, and in paying attention to that shift in degree from one end to the other. What you don't appear to have put much consideration towards however were the more obvious manifestations of foreshortening.

In cylinders, there are two signs that convey to the viewer the form's length (or more accurately, the distance between the two ellipses on either end of the form). There's the shift in degree - having a considerably wider far end relative to the closer end suggests that there's more distance between them, whereas less of a shift suggests that there's less distance and that the cylinder itself is shorter. Then there's the shift in scale from one end to the other, which is one of the basic things we know about perspective. As the farther end gets further away, it's going to be drawn smaller.

Both of these things are a part of foreshortening, and therefore they must line up. If the shift in degree is more dramatic (for example the cylinder at the bottom of this page), then so too must its shift in scale be equally noticeable. Otherwise you'd be communicating that the cylinder is both long and short, resulting in a contradiction that the viewer will notice, even if they can't necessarily pinpoint its cause.

The only other thing I wanted to mention about this section is just to remember the use of the ghosting method when drawing every mark. Your ellipses are for the most part quite well done, but as you continue through the set, the side edges tend to get just a little bit more hesitant, and I'm not seeing the usual tell-tale signs that you're following all three stages of the ghosting method. The marks themselves are not bad, of course - and the ones that come out a little worse are always longer, which do certainly pose an additional challenge. It's just worth noting that following through every stage of the ghosting method purposefully is what will help you most when tackling these more difficult situations.

Moving onto the cylinders in boxes, these are all largely looking pretty good. You've been very conscientious in applying your line extensions, and as a result, you've visibly improved in your ability to estimate how you'd have to draw your box in order for the cylinder contained within it to work correctly.

That is more or less what this exercise is about - instead of the cylinder being the focus, it is merely part of the analysis/correction step. Instead, here we learn to improve our ability to draw boxes that have two opposite faces which are proportionally square. This works because the lines we add to the line extensions for each ellipse will only converge towards the box's own vanishing points if the ellipses represent circles in 3D space that rest along the surface of the box. If those lines don't quite converge consistently towards the box's own VPs, then we adjust them slightly in our next attempts, gradually bringing them closer, and in turn improving our ability to draw those faces as squares in 3D space (since the plane that encloses a circle will always be a square).

In this regard you've done a great job, and you've been very diligent throughout. I did however notice that your submission appears to have been cut off, with the last page being the one marked 60/100. I'm ready to mark this challenge as complete, but I will need you to submit the last few pages to ensure that it is indeed finished.