I'll assume it's just me - and of course I don't want to insult anyone - but I cannot imagine telling someone to get out of an empty seat because I have the whole row blocked. While I wouldn't have said to pi$$ offf, I'd certainly have stayed there. I'm pretty sure I wouldn't even ask to have the whole row blocked in the first place. It can be great to stretch out, unless you've bought all those seats, I don't think you've got any more right to them than anyone else.

I'm 6'4" and would definitely book the J seat - however, not long ago, flew LAX-NRT in Y and was able to get quite comfortable with just 3 seats in the middle section. Was able to leave the woman on the other end 2 to sleep in.

Just a note - the arm rests on the 777 don't fold up flush with the seats, so laying out on them isn't as comfortable as it sounds.