It's a good idea to remove the ridge before knocking the pistons from the cylinders. If you don't you can damage the ring lands in your pistons. Plus, if you leave the ridge there and install new rings, the new rings could impact the ridge when it starts, damaging the ring lands or even breaking the new rings. One thing to make sure when using a ridge reamer is to stop at the top as soon as the old ridge is gone. If you keep going you will taper the top of the cylinder and cause a head gasket leak. Make sure you follow the directions for your reamer and they'll work as intended.