I'll look for Tall's diary, I haven't read it but I've heard of him. He was the 5'10 to 6'4 guy with Mahboubian I think. The thing is the few people who have done 15-20cm did it because they didn't care about losing athletic ability, they were resigned to it, so they never tried hard to recover it. (After that much LL, even recovering your walking ability is a struggle.) Crazy 6 is crippled, Greekster might be alright but he was so afraid of his proportions getting criticized that he never posted any pics or videos to show us. I think Apo made a good recovery, he's shown us him running on a treadmill, jogging on grass, and jumping on a trampoline.
My personal LL guideline is that if you don't exceed the total or daily elasticity limit of soft tissue, you're good. So don't lengthen over 8cm on femurs and 6cm on tibias, and NEVER faster than .66mm a day. If more people followed that, Shyshy and OBG and even MDOW wouldn't be the only ones to have made such great recoveries. Your bone might be able to regenerate at 1.25mm a day, but that doesn't mean your muscles and nerves can. Keep your femur to tibia ratio within reasonable limits. Preferably lengthen with a weightbearing method like the G Nail.