No idea how he got 15' from an 8' haft unless his arms are elasticated and when he thrusts they stretch an extra 7' 
When thrusting your arm will only add up to 2', by stepping forward thats another 1', so we're on 11'. You need to grip the haft at a point where it is balanced enough to be wielded comfortably without loss of control - precision is incredibly important with a spear. So lets say that he has a light spear and it can be gripped 1' from the butt whilst delivering enough power/speed/precision, so thats -1'.
So he steps into the thrust - 7' + 2' + 1' = 10'.
(all rough distance estimations of course - I don't have my spear anymore <sniff>)
Even then that might lead to over-extending which would leave you vulnerable, and I don't know if you'd get enough power to penetrate mail armour with a light, one handed spear - be able to stab and tear apart flesh easily if there's any visible. To penetrate armour you need one of the big boys, the 10' spears, two handed, 1'' thick haft. The power of those things are incredible. Can smash and mangle mail. I was once stabbed quite hard in the base of the spine by one - left me paralysed for a few minutes, face down on the floor. Couldn't move. Luckily the chap didn't put anything out of place or break anything but the impact... can still feel it in my mind.
When thrusting your arm will only add up to 2', by stepping forward thats another 1', so we're on 11'. You need to grip the haft at a point where it is balanced enough to be wielded comfortably without loss of control - precision is incredibly important with a spear. So lets say that he has a light spear and it can be gripped 1' from the butt whilst delivering enough power/speed/precision, so thats -1'. So he steps into the thrust - 7' + 2' + 1' = 10'.
(all rough distance estimations of course - I don't have my spear anymore <sniff>)
Even then that might lead to over-extending which would leave you vulnerable, and I don't know if you'd get enough power to penetrate mail armour with a light, one handed spear - be able to stab and tear apart flesh easily if there's any visible. To penetrate armour you need one of the big boys, the 10' spears, two handed, 1'' thick haft. The power of those things are incredible. Can smash and mangle mail. I was once stabbed quite hard in the base of the spine by one - left me paralysed for a few minutes, face down on the floor. Couldn't move. Luckily the chap didn't put anything out of place or break anything but the impact... can still feel it in my mind.
