Sorry about my poor english. I would try to be clear, ok ?!
I think that every person has different measures. The diameter of my head is 60 cm. Don´t call me "big head" , ok ?!!:lol
I´m starting to use Pepakura too, (really noob

) and I already read about "perfect scaling" and I think that each one says something different from the other.
The "perfec scaling" is that fits perfect in you. So...print...glue...test. Don´t fit perfect ? Increase the values and try again.
gives a lot of work, but at the end...Works !! :thumbsup
i hope i have helped you.
a hug and regards from Brazil.