I believe it was on this board where I read people lopping off dead coils on the springs, let me try to dig up a post
edit: heres one
I don't think that would work well with a Model M because the springs need a certain amount of tension to buckle. If you shorten the spring you'll basically end up with a linear keypress and a switch that never actuates.
The only way I can think of to do it is to use springs that are identical in every way (length, number of coils, and diameter) except the thickness of the wire used.
Or use a different, slightly more flexible metal (though I'd have no idea what, heh).