After spending a couple of hours each day for the past week, I've finished my Crack! It's technically not 100% complete (the shellac spray that I applied to the box has an "orange peel" texture that I want to try to rub out later; badge is in the mail; Speedball is awaiting installation in a few months), but I couldn't wait to plug it in and give it a spin.
I've attached a couple of photos, as I'm quite proud of how it turned out! I think that it actually looks better in person than in photos.
I also took some time to write a Reddit post to present some of the information that I've learned along the way, which might be helpful for beginners like myself:
https://www.reddit.com/r/headphones/comments/bkhqrc/a_beginners_guide_to_the_bottlehead_crack/ If you see anything inaccurate, please let me know and I can edit it.
Thanks very much to all of you for creating and maintaining a friendly and welcoming community. I appreciate the time and effort that you spend educating us newcomers -- I'm excited to try other audio projects...