Hi there sombes! Nothing much to say as you're already going to get critiqued by the TAs, but I have some things that might help you through the rest of your challenge.

Not sure if you have it solved yet, but you can basically put as much dots as you want, there is no limit. Checking things before drawing a line, is always good. As long as it's always you can always do, you can do everything. Mark dots to take account of where the direction of the vps are, or even using your pen to check convergences.

Your boxes feel pretty good to me already. There is only one thing I noticed, which is that you could try more rotations and orientations of boxes. I recommend trying more orientations of boxes, and giving it a shot at other boxes like 2p perspective boxes, which are helpful to practice as well. The Y generator helps with it as well.

In general you're doing a great job, so I think you should start with the advanced exercises as soon as you get your critique of the box challenge. The boxes on string are pretty cool because they make you start drawing boxes without using the Y method and are super useful, be sure you don't miss them.