The small wave springs I have found are very soft, they just give enough tension to push the clutchbell up and does keep the balls of the thrustbearing perfectly in the groove of the discs. The problem with to much play is when the clutch engages the balls of the bearing have to find the groove, at that moment a lot of forces are on the ring holding the balls and then after a few times the balls come loose...
I have these springs on all my clutches.

Another trick I have used for years is use a brass 10x5mm washer between the 2 steel discs, works perfectly and does not need any maintenance. You can find these brass rings at any hardware store at the screws section beside the steel screws and washers.