Cutting the spring is not a good idea. It will ruin any ride quality you have left after installing the RB springs. The RB springs are really nice and provide a combination of a balanced ride and more aggressive handling. You may want to call Racing Beat and ask them if they offer anything that's not in their catalog that may lower the rear a little more. Other than that, cutting those springs will ruin them.

 

I've cut springs before on my fc and the ride was fine. Never did it on the fb so no experience there, however, there are coilover kits you can to lower the rear to your liking.

 

You can cut one coil off to get it lower and it won't affect he RB springs that I can tell. Mine all have one coil worth cut off to get it down to the level I wanted. I'm running 15x7 Konigs with 205/50R15 Dunlops. Under heavy cornering I did get some light tire rub on the front fender lips. A little tweaking to bend the upper lips back a bit cured it. Cutting one coil will probably place you at the level you want. Just make sure to cut the coil from the spring end where the coils are closest together. Oh and chop your rear bump stops in half if you do this.

 

 

Post a pic of your car with the coils cut so the OP can see if that's the look he's after

 

You can also buy shorter rear springs from these guys Suspension Spring Specialist, Inc. They might be a little short, but you can always shim them. You just need to get the spring rate that is similar to the RB springs. The 8" are what I use on the back of my race car. It definitely drops the rear way down.

 

I'm pretty sure Racing Beat Springs were intended for a stripped down SA22C car running a lightweight intake/exhaust and rear mounted battery. That is the only explanation I can think of as to why the rear end will sit a good 2.5" higher than the front even after you let them settle for a few hundred miles. If you cut one coil, it will lower the gap to 1" between front and rear which is the correct specification mentioned in the workshop manual. Fill up your gas tank, double check your tire pressures, park on a level surface like your garage, and check the distances from the ground to centerline of the front and rear bumpers. Factory spec is 17.72~20.24" front and 18.66~21.02" rear and with the RB springs you want about 17 front and 18 rear. If you want to be careful, make some marks at 1/4 coil intervals and cut them a little at a time.