For the most part, your cylinders in boxes are done well - aside from a couple little instances and issues that I will address momentarily. Despite those, you do largely hold to the core principles of the exercise nicely. 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.

Here are the main things to keep an eye on:

• As before, there are a lot of cases here where you've forced vanishing points to infinity, resulting in too much parallelity in your side edges. Given that we're focusing with the line extensions on identifying how those lines behave as they converge, it does diminish that to a point. Fortunately this was not the case for all of your boxes, and you do have many that do have clearer convergences to them.

• Be sure to extend your minor axis lines back as far as the others, so we can more fully understand how they behave, and compare them to the others of their same set. Right now you appear to be applying the correction approach used in the first section of the challenge, so there may be some confusion there.

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