Excellent. You're getting more consistent with the proportions and they're feeling more solid. I've found some flows/abstractions that may help you gain even more consistency (See the attachment, since it's hard to describe in text). Next, it looks like there's some trouble finding the centerline of the bucket. I like to use the back third guide line (since it's closer to the edge of the ellipse and it's shorter) to compare with the axis of rotation; I'm thinking of how you find the center of a box in perspective when I look for the centerline. I'm also looking at the angles that form in the center to judge the centerline compared to the side-to-side line. The last thing is to avoid popping the top of the sacrum away from the iliac crest like you've done in the 3rd image, since they flow together so nicely. OK, sorry for all the text. Feel free to ask questions.

The biggest issue I see is that your ellipses don't always have the correct angle of rotation, and when the axis is off - your ellipses become ovals which is why they look squashed or out of perspective sometimes: Drawing the axis of rotation first then matching the ellipses to it may help you achieve the correct orientation. The other thing is that you need to make sure that the center of the sacrum is lined up with the center of the "bucket": having the back of the sacrum touch the back of the bucket form should help with that. Hopefully, my sketchy drawings aren't too hard to understand. If you have questions I'll try and get around to answering them.