There is a German Magazine plans site that offers one at about 8' span. The site is in German, but you can muddle through it. I tried to e-mail them to enquire about ordering these plans myself, but I had no reply. Since then, a fellow here at RCU posted an e-mail address that he said they will reply to in English, but I haven't tried it yet. Here's the web site: www.vth.de/modellbau/default.htm you'll have to look for the "store" or "shop" button, and go from there.
The e-mail is: [email protected]
As you will see, the fellow that designed this model has designed many of the giant scale models in their range, which tells me he must be a decent designer. The plans are only $20 euro, so about the same in USD....quite reasonable, I'd say.
Good luck, and please let me know what you find out, as I'd still like to get a set of these plans myself...thanks!

Cheers, Nigel

PS If you can't find the plans, give me your e-mail address, and I'll e-mail a direct link to the plans page with the Comet.