Our holiday is July 1, Canada Day
Hope the fire works are good
I allowed for 3 plates which is two top plates and one bottom, Only use one top plate if your rafters can land directly above a stud. We never go with one top plate.
I went with 107" so you wouldn't have to buy 10 ft 2x4s.
Sounds like you have the math down anyway, some cities up here measure the height half way between gutter and peak, that would give you another 8", might be worth checking.
2/12 is a very low pitch.