I have a Kohler K-9132 shower drain I'm trying to install. The last step is to install the big gasket that makes the seal between the drain housing and drain pipe. I got this gasket about 3/4 of the way inserted, still have about a half an inch to go and it will not move anymore. The whole "soapy water lubricant" thing in the instructions didn't seem to help much. I've tried working it with a wood shim, but I've gotten as far as she'll go it seems.

Any advice? Is there enough in there for a good seal and I can just trim off the last half inch?

Thanks much!