Starting with your cylinders around arbitrary minor axes, these are alright. You have certainly taken care in identifying the true minor axes here, and I can see that you've included a variety of rates of foreshortening throughout your work.

When it comes to your linework, it varies, and I think it does so based on how much time you put into executing a given mark. You've got some ellipses that are quite tight and well executed, like those in cylinder 63. Others, like those in 85. would definitely benefit from investing more time into the planning and preparation phases of the ghosting method. There's similar variation in the straight lines you use for the side edges, although I do feel that these improve more noticeably as you push through the set, with the earlier ones being a bit more rushed, and those later on being better planned out.

One thing I did want to call out here is that while you're certainly playing with the two ways in which foreshortening manifest in our forms. One is the shift in scale, causing the end closer to the viewer to be larger than the end farther away. The other is the shift in degree/width, where the farther end is proportionally wider than the end closer to the viewer. I can see various examples of you applying both of these.

What I want you to keep in mind is that since both of these help us convey the rate of foreshortening to the viewer - that is, it's how we tell the viewer that the form is tilting more or less towards them through the depth of the scene - both of those shifts have to work in tandem. When we have a more significant shift in scale, but no visible shift in degree like cylinder 92, it will end up looking off, because there are two distinct things being communicated to the viewer. Make sure that when you've got more dramatic shift in scale, you also include a more dramatic shift in degree, and vice-versa.

Moving onto the cylinders in boxes, I did notice that a lot of these seem to limit, or outright eliminate, the convergence of the sets of parallel lines. There are definitely some that include more convergence, so I'm glad to see those, but I really can't stress this enough - while shallow convergences are fine, you need to make sure that you're not drawing sets of lines that are parallel with one another in 3D, as being parallel on the page as well, unless those lines run perpendicular to the viewer's angle of sight. So basically, if you've got lines that run straight across from left to right, up to down, or whatever without slanting towards or away from the viewer at all, those can be drawn with an "infinite" vanishing point. Anything else must be drawn with convergence.

I am glad to see that this time around is that you've correctly applied the line extensions here - or at least, mostly correctly. From what I can see, you might not be extending your ellipses' individual minor axes, so make sure you do that when practicing these in the future. Being sure to extend all three lines for each ellipse (minor axis + 2 contact point lines) is what allows us to see how far off they each are from representing circles in 3D space, and how far off the planes that enclose them are from representing squares in 3D space.

I am going to go ahead and mark this challenge as complete. I've outlined a number of things for you to work on, but I feel you can tackle those on your own.