I believe the $1 level is also important. The more the better. I would like to see thousands of $1 pledges as it indicates a greater level of interest.
BTW, I voted 1 free aircraft. I can't see the backers becoming offended at this and backing out if it is explained clearly. Non backers will have a similar opportunity to discover the value of the sim as in DCS world with the one flyable. That's how I came in and started buying modules. Try one free buy the rest but if you've got the whole stable free at the start why buy or back for that matter.
@"when in doubt go with integrity." I'm sure a lot of non backers will agree with you as they gleefully fire up their free airplanes.