Kinda depends on what shape the springs are in to start with. If they're already shorter than spec, they've started to sag. Cutting them shorter will stress them more (fewer coils to bear the load) and they'll likely really sag then. If they're fresh, it might work, but you've gotta watch out for coil binding. If the suspension travel compresses the spring sufficiently that all the space is used up between the coils, the suspension will bottom VERY harshly, and perhaps damage some parts (I doubt the top caps are designed to handle that much stress). Cutting a coil or two would probably be OK, but much more is likely to lead to trouble. You'd need to measure distance from spring seat to seat, fork fully extended and fully compressed, measure the spring wire thickness and gap between coils, deduct spacer length, and see if there will be any gap between coils at full compression. By the time you do all that (twice, to make sure there's no mistake), then cut a couple of coils, bend, grind and polish a new end on each spring (so you don't tear up the seats), clean the springs very carefully (filings in the damper assembly are bad), make new spacers, and maybe find out you still don't have enough stiffness, you might have been better off buying new springs of known stiffness that come ready to drop in. Unless you are really short of money, and have a lot of time on your hands.