Nando: I'm glad you enjoyed the D-21! I had been looking for one for awhile too, before I started designing models, so when I decided to do the SR-71, and then got into it's variants, the D-21 was an obvious choice. Finding useable reference images on the other hand was slightly difficult.
Sorry about the bottom fuselage too, I noticed when I built it that I forgot to make it black (Doh!). I'll probably upload a fixed version of it sometime today. I also appologize for the need to make adjustments with my models...I tend to leave some flaws in, and some of the models lack accuracy sometimes. I'd appreciate a small list of the issues you found with it, so that I might make some modifications to the file to allow easier construction for everyone else.
Lex: Don't worry, they're coming! I never posted images of the completed prototype because I never completed it. I built one engine of the prototype, but never a second, mostly because that was all I needed to assemble to test the design. I finished up the paintjob for the USMC model and printed it out. As it is, I have one more engine to construct and the model will be done. Just to let you all know, the rotor tilts and spins. I was actually able to achieve a loose enough axel that you can blow on the blades and they spin, with nothing but cardstock! I myself am not a card "purist", when I make modifications I use whatever I can get my hands on that is cheap, but I figure I might as well make models that can be assembled with nothing but paper, for those of you who are purists.
Speaking of the axels, I never included the parts for them, just a warning. I guess I sort of figured I didn't need too, since all you have to do is roll some paper. I'll probably update the PDFs to include some basic shapes for the axels though. I also took pictures of most of the construction process, and should be posting those somewhere on the forum, just in case some aspects of construction aren't clear.
Anyway, hopefully that second rotor will be done in an hour or two (making this model the longest to construct of all I have designed so far).