Do you have any positive or negative conclusions to your MAF training?
I made good progress and liked training by HR. My power and pace gradually increased at the same HR so it was happening naturally instead of just forcing it by a pre-determined plan. I also liked that I saw constant improvement and didn't have to wait for a test day to see if I've improved. My big problem with Maffetone is the 180 formula. For me, it puts me in Joe Friel's HR zone 2. For other people it will have them at a much lower intensity level (Ken, for example, would be in Zone 1 even though his heart rates are very similar to mine - Tim would be even lower because his heart rate tends to be almost 10 beats higher than me and Ken so we could all do Maffetone training yet we'd all be at different intensity levels) and I question if you'll get the same gains going that easy everyday. To me, it makes more sense to use HR zones based off threshold or maybe max HR.
I agree with your thoughts on having to modify the HR to the individual person. As I train with Ken we usually have about a plus/minus 15 to 20 HR rate difference. and even yesterday doing the 70% to 75% ftp ride we were 30 HR apart. It seems like a person needs to determine at what HR or % ftp to set as your base.