To answer your questions first:

• Yup, no problem with that. Just make sure that you get your credit before decreasing your pledge.

• You can go ahead and use ballpoint for those if you wish.

Starting with your cylinders around arbitrary minor axes, your work here is quite well done. You're fastidious in checking the true alignment of your ellipses, and your linework is fairly decent. Some of your ellipses do get a little more hesitant and fall a little off track, but I think this is simply a matter of slipping back to using your wrist more - so just remember to always engage your whole arm when drawing your ellipses, while using the ghosting method to improve your overall control.

I noticed that you were particularly careful about ensuring that as you shifted into more rapid convergences, you increased the rate at which the degree of your ellipses shifted - basically, as that far end ellipse got smaller in scale, you also increased its width to match. This shows a strong grasp of how these different "shifts" work together to convey the rate of foreshortening to the viewer. There is however one thing I wanted to call out on that point.

When you've been drawing particularly foreshortened cylinders here, you've been starting the end closest to the viewer as being very narrow. While this is technically correct, keep in mind that the foreshortening conveys two things to the viewer - one is the scale of the object itself, and the other is its orientation in space, how much it's tilting towards the viewer. When you're shifting from such a narrow ellipse at the front end, you're pushing the idea that this cylinder is huge, so much so that it experiences considerable perspective distortion. Like I said - it's still correct, but it's not necessarily what you're after each time.

If that closer ellipse was wider, it'd suggest more that the cylinder was coming towards the viewer. This would still fall within the bounds of the correct "degree shift", simply because you can only get so wide. Once your cylinders start pointing towards the viewer, the extent to which the degree can get wider gets very limited - but that's totally normal, and it just means that towards that wider end, a slight shift in degree is more significant.

Moving onto your cylinders in boxes, I think you've definitely shown a good bit of growth and improvement here - though there's always room for more. This exercise is all about develipg students' instinctual ability to construct boxes that specifically feature two opposite faces which are proportionally square. We do this by, page after page, checking how far off our ellipses are from representing circles in 3D space, and therefore how far off the planes that enclose them are from representing squares. All this plays off the same line extension approach from the box challenge, with each ellipse bringing three more lines - the minor axis and two contact point lines. We can test whether they're circles/squares, or rather how far off they are from being so, by checking how far off the ellipses' lines are from converging towards the box's own vanishing points.

While I do think this was somewhat touch and go for the first half, and perhaps more, of this exercise, I think that by the end of it you definitely solidified your grasp and started making more notable improvements. What's important here is that you'v been extending all of those lines - some students get confused with the previous section, and only end up marking out their minor axes without the appropriate extension.

Anyway, you've done well overall. I'll go ahead and mark this challenge as complete.