I'm a DAR in the Northwest. "Major portion" or the "51%" rule is a bit grey. Any evidence that a builder can produce such as photos, build logs, build manuals with notations and dates, etc. can serve to comply with the order. Another grey area is the commercial "educational" assistance. Paying another to assist in the build in most cases is commercial assistance, and is subtracted from the major portion. Paying someone for educational assistance and guidance is allowed by the order. It is up to the ASI or DAR to make the determination at the time of inspection. Several "Kits" have been evaluated by the FAA "NKET" team, and based upon their evaluation, one can determine how much commercial assistance can be purchased and still be in compliance. For non "NKET" kits and plans built, the 2011 "51%" checklist is a good guide.