moved my question to appropriate forum
Sounds like you need a new spring. By stretching the spring I would guess you have upset the balance of the stick, since it is now not a uniform shape. There is also the chance that spring end is digging into the actuator. PAS sells many different springs http://www.paradisearcadeshop.com/632-springs if you want something to stiffen up a JLF I would start with the 2lbf.