Well, it only took me 2-1/2 months, but - as of last weekend - the Greenhouse Structure is DONE (Yayyyyyy!!!).
I've posted pics, observations, and Garden-Webbers' hints 'n links (Thanks to ALL!) on my website. Maybe this will help others who are considering purchasing the 6x8.
Important Note for Newbies: HF's instructions *have* improved (a bit) - but I couldn't have done it without conifer's pictures. Well, maybe I could have, but there would've been a lot more swearing going on!
Oh: And NO! It shouldn't take 2-1/2 months to build! I just wanted to take my time, do as much of it "solo" as possible (to minimize the "Jerry Springer Moments!"), and generally not stress-out over it...
Overall it was surprisingly easy to build, all of the pieces were "there," they do fit together nicely, and it's da*ned sturdy IMHO!
Next Steps: "Accessorizing!" And yes, I've started a separate webpage for that, as well...
Anyway - I just wanted to share. And say THANKS again to all of you for your wonderful advice!