Best way to do a lowering experiment?

[MetroMPG]

Can anyone think of a way to do an A-B (at minimum) lowering experiment on my car, where the runs could be immediately before/after?

I tried doing this...



...by jacking up one corner of the car until the opposite suspension was as compressed as possible, then wrapping cord around the spring (I managed to tie together 4 coils).

When the jack was removed, the cord held the spring about 1 inch lower than stock. It actually held for a week or so, then broke rebounding on some bump.

Is there any other easy & inexpensive way to go about this?

I also tried using muffler-style clamps on the spring itself, but they wouldn't stay in one spot (jangled over bumps)