No need for a documentary film. We've seen/heard this a bunch of times before. Why? Who knows? Maybe the bore in the back of master cylinders varies in depth.
We've seen the return spring rigged under the dash before too. There isn't a proper place for it. Going to drill holes for eye screw attach points? "Rigging" anything about brakes is not safe. That spring just might pull the rod out of the master cylinder someday. Add the fact that the added pedal travel before braking will feel like air in the system or something waaaay out of adjustment.
There is some adjustment at the switch bracket. There are adjustable pushrods. Enough said.
Good luck with it.
