For flattening, have you tried the “unwrap and flatten faces” plugin by alexschreyer ? I have installed this, and it works fairly well, but I haven’t employed it for final product yet. This may, or may not, assist you in accuracy, as it doesn’t require export of your SU drawing to another software program to flatten.
Additionally, a question, I cannot find the “joint push pull” plugin that you mentioned. Can you suggest a search term, or is it part of a suite of plugins?