What mine does is: when you pull out the strap it will go forward w/o stopping unless you stop the motion. If so you have to reset it back all the way retracted. But as long as you pull it forward in one motion you're good to go. So it's best to take the strap with one sweeping motion and pull it all the way out and then you back track it to the adjusted position. Now on the return, if you snap release it, it will retrieve all the way back into the retractor and ready for it to pull forward again. If you slow release it, it will retract all the way back into the retractor except for about 6" of strap (length not including the buckle). But you still can assist the remaining strap back into the retractor to the position where you can pull it out again.
If you're rigging something to hold back the spring you're defeating the purpose of what the seat belt is designed to do. Yes it will satisfy the cops if you get pulled over, showing them that you are wearing your seat belt. But restraint is not there.
My 2¢