Mine required quite a bit of force to change. I played with it when I first got it, changing them and ended up putting the original one back on. You want a lot of force to remove the sole, as it will keep the thing on better when you're actually wearing them and sliding.
If the Cabrettas came with the metal pick (I think it's the cleat pick, so maybe not), you can use that to pry up an edge. Do the Cabrettas have a ring of felt around the outside (i.e., the replaceable part doesn't cover 100% of the sole)? If so, it's tough. If not, then you should be able to get it started at the very edge.
SH
