it just feels very loose and doesn't seem to be doing much in altering the action (which is fine because with the strings i like the neck is straight enough).
With the truss rod loose, which is what it sounds like is going on there, it is not doing anything to counteract the tension the strings put on the neck.
Sounds to me like you don't have anything to worry about.
Take it to a pro to get it set up. Though i have just bought an OLP neck off ebay to go on a SUB body i'll be buying off someone soon. In theory it SHOULD fit, but i can't be bothered to try it on my current SUB