Last weekend I picked up 2 boards... one 14' DW and one 12' Touring.
I strapped 12'er on top of the 14'er on my Honda Civic (compact)
I stack nose forward and down, because I want the wind pressure pushing the boards
down onto the rack, rather than lifting or neutral.
Drove 386 k at 120 kph with no worries.
ha ha.... how about 650 km with 8 boards in boxes.... shortboards, but boxes have a lot of wind resistance.
Strapped with rope only