Starting with your cylinders around arbitrary minor axes, there's a lot in your set that is coming along well, but there's also a very prominent sign that you did not go through the instructions as carefully as you could have. These reminders (specifically their second point) make it very clear that you should not be forcing your cylinders' vanishing points to infinity, but across your set you do this a lot. It shows up most of all earlier in the set, but we can even see it occurring further into your work, like 124 and 127 on this page, you still do it on occasion. Be sure to avoid this in the future - as explained in those reminders, we can't simply decide to make a set of edges converge to an infinite vanishing point. This only happens when the orientation of those edges allows it to. This is also discussed further in Lesson 1's boxes section.

Aside from that, your work here is largely well done - your linework is fairly confident without a ton of hesitation, allowing for smooth lines and evenly shaped ellipses, and you're doing a good job of fastidiously checking the alignment of your ellipses' minor axes.

Continuing onto your cylinders in boxes, that same issue of forcing your vanishing points to infinity does show up early on and actually seems to cause you a lot of trouble as it results in some notable confusion as to which direction you should be extending your lines. You seem to be trying to force all your vanishing points to infinity to achieve a sort of "0 point perspective" - note that this section from Lesson 1 talks about why 0 point perspective doesn't exist. Fortunately you shift away from this approach fairly quickly, so it doesn't end up messing with your work very much.

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.

Overall you've been holding to this fairly well, although I do have just one small thing to bring to your attention - when you're extending each individual minor axis for each ellipse, don't stop that extension early. Extend it all the way back as far as the others, so that you can very easily and quickly compare how their convergences behave at a glance. When you stop short, it adds that much more of a barrier to glean the information we're after. It may not seem to be that significant, but when dealing with as many of these as we end up drawing in the fullness of time, the little bit we extra we gain (or more accurately, the less of the benefits of the exercise that we lose), the better.

I'll go ahead and mark this challenge as complete.