Walter,
interesting problem. I had the opposite problem at the rear and had custom springs made. I needed to increase ride height by 1/2 inch. I measured the springs installed, then measured them removed, and found that the installed height was about half of the free height. So I had the custom springs made 1 inch longer, figuring when they compressed I'd get a half inch more ride height. It worked out about right, but your case is rather more complicated.
I think you could do something similar, but you need to figure in the suspension geometry. If the spring sits halfway beween the inner and outer joints on the lower control arms, then the ratio there is 2:1. In that case, you'd need 1 inch less installed spring length to get a 2 inch drop. Then you'd have to somehow measure the installed spring length versus the free length, and use that ratio to figure out how much to cut off. This is approximate, but should get you close. The front springs are quite long, and I'd guess you could cut off a lot before they became loose at full droop.
Cutting the springs will make them stiffer, and with less weight up front plus stiffer springs, the overall front suspension stiffness could increase pretty significantly. If the rear is not stiffened up at the same time, you could get some unpleasant ride effects, like a tendency to pitch over bumps and maybe strange handling. If you want the car to ride "normally", you really need shorter and softer front springs, not shorter and stiffer. This gets into a more complicated design procedure to figure out the desired spring rate. The book "How to make your car handle" by Fred Puhn might be helpful if you want to go this way.
Not sure this has been all that helpful... but good luck, and if you need front spring data, let us know.
George Davis
'69 280 SL Euro manual
