I've just done this mod this morning. Although the SE springs are 1/2 an inch shorter than the stock 990 ones, they fitted fine without spacers, ending up just compressed slightly with the preload wound all the way out. A Mooky says you need to take out the hydrostop and file it down a little so it slides through the spring ok. I had a bit of a panic as one of these was binding and wouldn't unscrew from the damper rod, a pair of circlip pliers down the inside of the rod to hold it still did the trick though.