Installed head on the F engine for good.
OK, not true. Installed the head and realized I did not check if the 2 O-rings are in place - they always stayed there, but I did not want to take the chance so I pulled it off again.
Long story short, the o-rings were there, happy as ever, but would you assemble an engine with a shred of doubt?
Head is installed, torqued, ready for towers.