I'm also a perfectionist when it come to this stuff so i totally know what ya mean. my reasoning with using the interior panel lines are to make it very close to perfect and from there its systematic just build both rings at the same time (make 2 of everything and tweak from there till it is perfect) since my car will be in a heated garage while i do it. weather sucks here!
it will be my first time as well with fiber glass so gotta do it right.