VT, I'm pretty low at the moment. I fell whilst out running on holiday 11th November. I have badly damaged my hamstring on my right leg.I hit a raised flag with my left whilst jogging downhill, and kicked out with my right, right at the end of my run. I was 200yds away from the apartment! From reading the internet, it is a grade 3 strain, and could take 12 weeks!! I am in constant pain and the whole leg is bruised and swelled right down to the ankle. Obviously doing the ice thing but it's not easy whilst at work. I will post a pic of the hammy shortly.
Ecce, don't worry - the phased approach to 80% runs are fine and I would say the main reason for this approach is to allow the legs (and mind) cope with the longer spells of moderately hard running. I find that after a break, the 80% doesn't improve until I get to the longer single efforts, probably upwards of 50mins. So if I were you I would plough on with your approach, and be patient, the 80% improvement will flow when you get to 70mins.