Here's something that's been bothering me. The "major portion" / 51% rule has certainly been discussed a great deal in aviation circles, but I still don't know, how far can you push the rules. Tools are what I'm thinking of now. Say you need a custom tool to build an aircraft. I think Zenith wants you to use a special nose for a rivet puller, so let's use that example. If the company lent you the tool, there would be no question, obviously, that any work you do with it is still yours. If you need a jig for welding tubes, or if it's a composite aircraft that needs molds, I assume that you can rent, borrow, or buy the tooling from someone - since it's not part of the aircraft itself, you can't argue it's detracting from your contribution. Similarly, I assume that nothing prevents the kit manufacturer from renting out (or simply letting you use) their space. So you could layup their kit into their molds in their building, and you haven't changed the amount of work you do. Now, imagine you're really rich, and you want to build your airplane by buying a CNC tape layer. No problem there, you still do it all, right? Ok, one step further. Can you build your airplane in someone's factory, by pushing the button to lay tape over their molds, using their winder? Sounds like it should be "no!" -- why? What's the line? *I realize that even if all the parts are laid up by machine, etc., there's still a tremendous amount of work involved in putting together the aircraft. But, would those parts count as things you built, when you are tallying up the division of the construction?