Hey there, hope you don't mind my over-drawings, I think you have a nice grasp on construction, just wanted to point out how using 2 point perspective on that last piece can help it look a bit more convincing to the eye. Note, i think you can easily get away with eyeballing it but it definitely helps using vanishing points for ease and accuracy.

You see, as it is, it's isometric - everything tends towards parallel and some of the lines are off (not parallel to each other in X Y or Z).

So by adding a horizon line and a couple of vanishing points it can help you with getting all the accurate angles for a more convincing looking 3D object, in this case all verticals are parallel but the other lines will converge either to point 1 or 2, and i subdivided some planes to help make the curves

perspy.png8307x2513 723 KB

As for cylinders, you can construct them within boxes when drawing them in perspective

cheers!

Looking good. Keep at it and try adding in the torso and heads.

One thing to note, whenever doing exercises I personally feel the presentation can suffer if anything is sloppy, for example, when siggesting the shade on the fkat side of the cylinder, rather than squibbly lines try a consistent parallel hatching and be mindful of line weight, if its less important on your mind - say it in your work, else no one can read it as such. Its like a language, if you want to show that your side plane is less important for you you could add some straight parallel lines super lightly, but if in stead we have a thick squiggle that is unlike anything else on canvas - it reads differently. That took me a while to understand, always keep an audience in your mind and imagine you are trying to tell them everything in your mind kinda thing XD

Cheers