If you do use the second line up as full make sure you measure when the fluid is hot. Even then you can expect the get some fluid escaping through the cap on any driving with hard turns (track or canyon). Not a lot but some.
Personally I use the first line and fluid at ambient.
2015 BMW M5 Sedan M-DCT w/Competition Pkg and Carbon Ceramic Brakes, Driver's Assistance, and Executive Pkgs, B&O, Alpine White / Sakhir Orange and Black Full Leather, lots of carbon fiber, and a Trunk Monkey call "Der Stig".