Zizka's Sketchbook (Nudity and Vulgarity, NSFW)

[Who]

Dunno if this helps, but the excercise in drawab which first gets you to draw a square in perspective and then plot the circle within, is the more technical way of resolving the cylinder end caps. You can think of it as drawing the bounding square and or entire bounding box for the cylinder in perspective because it's simpler, THEN draw in the ellipses using the square ends if you need a guide.
Drawn in blue here.

The purple end cap at the other end, is a duplicate of the other end cap. Notice it doesn't fit the bounding box of the cylinder. That's because of perspective distortion, hence there is convergence towards the vp and the whole end cap appears smaller.

Another way you can think about judging sometimes is, if the end cap looks too 'fat' or is facing us more, the angle is too great, reduce it. If the cap looks too thin, or appears turning away from us too much, increase the angle.

This technical shit is good to help understand and for troubleshooting, but it is stiff and stifling when it comes to drawing them intuitively. So keep practicing eyeballing first and making it look as "right" as possible first (using bounding boxes as well if needed) but then go back and check how close your estimations of the actual minor axes of each end cap ellipse aligns, and it should show you what you are consistently getting wrong. This is all described in the 250 cylinder page I believe from memory.




ps. I haven't forgotten about the drawing. Gonna pm you soon