Constrained killzone problem

B1984

My constrained killzone worked... but randomly. Sometimes it was right where i want it and other times I die before I even get near it.

this is a screenshot of my attributes for a 128x32 player character
http://i6.photobucket.com/albums/y246/BranDoom21/Capturehook_zps48ae2832.jpg

and this is a ss of the attributes for the 306x16 enemy where I only want the bottom 8px to be deadly
http://s6.photobucket.com/user/BranDoom21/media/Capture_zps448075e5.jpg.html?filters[user]=4926598&filters[recent]=1&sort=1&o=1

Now, this is after an hour of tinkering with random numbers, so the original that worked somewhat are long gone. Does anyone have any clue how constrain a killzone effectively?